Document:

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                                                                   EXHIBIT 10.13

                            FIRST AMENDMENT TO THE
                 SECOND AMENDED AND RESTATED CREDIT AGREEMENT

     THIS FIRST AMENDMENT TO THE SECOND AMENDED AND RESTATED CREDIT AGREEMENT
(the "Amendment") dated as of January 5, 2000 is executed by and among IMCO
Recycling Inc. ("Borrower"), the Subsidiary Guarantors to the Credit Agreement
(hereinafter defined), the Lenders to the Credit Agreement and Chase Bank of
Texas, National Association ("Administrative Agent"), in its capacity as
Administrative Agent under the Credit Agreement.

                                   RECITALS:

A.   Borrower, Subsidiary Guarantors, Lenders and Administrative Agent are
     parties to that certain Second Amended and Restated Credit Agreement, dated
     as of October 25, 1999 (the "Credit Agreement"), pursuant to which Lenders
     have made revolving credit commitments to Borrower in the amount of up to
     $250,000,000.

B.   Borrower, Subsidiary Guarantors, Lenders and Administrative Agent desire to
     amend the Credit Agreement in accordance with the terms hereinafter set
     forth pursuant to the amendment procedures specified in Section 12.04 of
     the Credit Agreement.

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, and other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto hereby agree as
follows:

     1.   Defined Terms.  All capitalized terms used herein and not otherwise
defined shall have the meaning given to such term in the Credit Agreement.

     2.   Amendment to Section 9.10(b)(i) of the Credit Agreement.  Section
                       ------------------                           -------
9.10(b)(i) of the Credit Agreement is hereby amended by deleting Subsection
----------
9.10(b)(i) in its entirety and replacing it with the following:

          "(i) purchases by Borrower of shares of its common stock, provided
     that the sum of the aggregate amount expended by Borrower for such
     purchases, plus the aggregate amount expended by Borrower for purchases of
     its common stock during the period from and including September 8, 1998 to
     and including the date of determination shall not exceed $35,000,000,"

     ;so that following such amendment, Section 9.10(b) of the Credit Agreement
                                        --------------
reads in its entirety as follows:

          "(b)  the following Dividend Payments shall be permitted so long as no
     Default or Event of Default shall have occurred and be continuing at the
     time of such Dividend Payment nor would result therefrom:  (i) purchases by
     Borrower of shares of its common stock, provided that the sum of the
     aggregate amount expended by Borrower for such purchases, plus the
     aggregate amount expended by Borrower for

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     purchases of its common stock during the period from and including
     September 8, 1998 to and including the date of determination shall not
     exceed $35,000,000, (ii) prior to the issuance of the Subordinated Debt and
     the Trust Preferred Securities, if any, Borrower may declare and make cash
     Dividend Payments on its capital stock (other than purchases of its common
     stock permitted by clause (i) above) not to exceed in the aggregate
     $6,000,000 in each of fiscal 1999 and fiscal 2000, and $8,000,000 in any
     fiscal year thereafter, (iii) after the issuance of the Subordinated Debt
     and the Trust Preferred Securities, if any, Borrower may declare and make
     cash Dividend Payments on its capital stock not to exceed in the aggregate
     $8,000,000 in each of fiscal 1999 and fiscal 2000, and $11,000,000 in any
     fiscal year thereafter, and (iv) the issuer of the Trust Preferred
     Securities may make scheduled Dividend Payments on the Trust Preferred
     Securities."

     3.   Amendment to Section 8.13 of the Credit Agreement.  Section 8.13 of
                                                              ------------
the Credit Agreement is hereby amended by adding the following clause to the end
of the first sentence:

          ", except for stock purchases expressly permitted by this Agreement,
     so long as such purchases do not result in a violation of Regulation T, U
     or X."

     ;so that following such amendment, Section 8.13 of the Credit Agreement
                                        ------------
reads in its entirety as follows:

          "8.13.  Use of Proceeds.  Neither Borrower nor any Subsidiary is
                  ---------------
     engaged principally, or as one of its important activities, in the business
     of extending credit for the purpose, whether immediate, incidental or
     ultimate, of buying or carrying Margin Stock and no part of the proceeds of
     any extension of credit hereunder will be used to purchase or carry any
     Margin Stock, except for stock purchases expressly permitted by this
     Agreement, so long as such purchases do not result in a violation of
     Regulation T, U or X.  On and after the date hereof, Borrower will use
     drawings under the Revolving Credit Commitments for (i) ongoing working
     capital and general corporate requirements of Borrower and its
     Subsidiaries, including the issuance of Letters of Credit; and (iii) the
     financing of permitted Acquisitions."

     4.   No Further Amendments.  Except as modified and amended by this
Amendment, the Credit Agreement shall remain in full force and effect with no
other changes or amendments.

     5.   Counterparts.  This Amendment may be executed in counterparts and by
different parties on separate counterparts, each of which shall constitute an
original, and all of which together shall constitute one and the same Amendment.
This Amendment may be validly executed and delivered by facsimile or other
electronic transmission.

     6.   Expenses.  Borrower hereby agrees to pay or reimburse all reasonable
out-of-pocket costs and expenses incurred by Administrative Agent and the
Lenders in connection with the preparation, execution and delivery of this
Amendment, including but not limited to reasonable attorney's fees and expenses.

     7.   Ratifications.  Borrower (a) ratifies and confirms all provisions of
the Credit Agreement as amended by this Amendment, (b) ratifies and confirms
that all guaranties, assurances and Liens granted, conveyed or assigned to
Administrative Agent under the Basic Documents (as they may have been renewed,
extended and amended) are not released, reduced or otherwise adversely affected
by this Amendment and continue to guarantee, assure and secure full payment and

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performance of the present and future Obligations, and (c) agrees to perform
such acts and duly authorize, execute, acknowledge, deliver, file and record
such additional documents and certificates as Administrative Agent may
reasonably request in order to create, perfect, preserve and protect those
guaranties, assurances and Liens.

     8.   Representations.  Borrower represents and warrants to Administrative
Agent and Lenders that as of the date of this Amendment (a) all representations
and warranties in the Credit Agreement are true and correct in all material
respects except to the extent that (i) any of them speak to a different specific
date or (ii) the facts on which any of them were based have been changed by
transactions contemplated or permitted by the Credit Agreement, and (b) no Event
of Default exists.

     9.   Effective Date.  The agreements and amendments set forth herein shall
not be effective until executed by the Obligors, the Administrative Agent and
Lenders which constitute "Majority Lenders" as defined in the Credit Agreement,
whereupon this Amendment shall become a binding agreement, enforceable in
accordance with its terms.

                                   * * * * *

     EXECUTED as of the 5th day of January, 2000.

                              OBLIGORS:

                              IMCO RECYCLING INC.

                              By:
                                  -----------------------------------
                              Name:   James B. Walburg
                              Title:  Senior Vice President

                              IMCO MANAGEMENT PARTNERSHIP L.P.
                              By: IMCO Recycling Inc., its General Partner

                              By:
                                  -----------------------------------
                              Name:   James B. Walburg
                              Title:  Senior Vice President

                              IMCO INDIANA PARTNERSHIP L.P.
                              By: IMCO Energy Corp., its General Partner

                              By:
                                  -----------------------------------
                              Name:   James B. Walburg
                              Title:  Vice President

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                              ALCHEM ALUMINUM, INC.
                              ALCHEM ALUMINUM SHELBYVILLE, INC.
                              B & F METALS, INC.
                              GULF REDUCTION CORPORATION
                              IMCO ENERGY CORP.
                              IMCO INTERNATIONAL, INC.
                              IMCO INVESTMENT COMPANY
                              IMCO RECYCLING OF CALIFORNIA, INC.
                              IMCO RECYCLING OF IDAHO INC.
                              IMCO RECYCLING OF ILLINOIS INC.
                              IMCO RECYCLING OF INDIANA INC.
                              IMCO RECYCLING OF MICHIGAN, L.L.C.
                              IMCO RECYCLING OF OHIO INC.
                              IMCO RECYCLING OF UTAH INC.
                              IMSAMET, INC.
                              INTERAMERICAN ZINC, INC.
                              METALCHEM, INC.
                              MIDWEST ZINC CORPORATION
                              PITTSBURG ALUMINUM, INC.
                              ROCK CREEK ALUMINUM, INC.
                              U.S. ZINC CORPORATION
                              U.S. ZINC EXPORT CORPORATION
                              WESTERN ZINC CORPORATION

                              By:
                                  -----------------------------------
                              Name:   James B. Walburg
                              Title:  Vice President of each above-named
                                      Obligors

                              LENDERS:

                              CHASE BANK OF TEXAS, NATIONAL ASSOCIATION, as
                              Lender and Administrative Agent

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

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                              BANK OF AMERICA, N.A., as Syndication Agent
                              and a lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              MERRILL LYNCH CAPITAL CORPORATION,
                              as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              BANK OF TOKYO-MITSUBISHI, LTD,
                              as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              BANK ONE, NA, as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              PNC BANK, NATIONAL ASSOCIATION, as Documentation
                              Agent and a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              DG BANK DEUTSCHE
                              GENOSSENSCHAFTSBANK, AG, as a Lender

                              By:
                                  -----------------------------------

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                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              FIRST AMERICAN NATIONAL BANK, as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              NATIONAL CITY BANK, as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              AMSOUTH BANK, as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              COMERICA BANK, as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                              WELLS FARGO BANK (TEXAS), NATIONAL ASSOCIATION, as
                              a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

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                              BANK HAPOALIM, SAN FRANCISCO BRANCH, as a Lender

                              By:
                                  -----------------------------------
                              Name:
                                   ----------------------------------
                              Title:
                                    ---------------------------------

                                       7<PAGE>

                                                                   EXHIBIT 10.16

                         REGISTRATION RIGHTS AGREEMENT

     THIS REGISTRATION RIGHTS AGREEMENT (the "Agreement") is made and entered
into as of July 21, 1998, by and between IMCO Recycling Inc., a Delaware
corporation (the "Company"), and the Stockholders (as defined below).

                                   RECITALS
                                   --------

     WHEREAS, the Company and the Stockholders have entered into a Memorandum of
Purchase and Sale Agreement dated July 21, 1998 (the "Purchase Agreement"),
pursuant to which the Company has acquired all of the issued and outstanding
capital stock of U.S. Zinc Corporation, a Delaware corporation; and

     WHEREAS, pursuant to the Purchase Agreement, each of the Stockholders has
acquired shares of the Company's common stock, $0.10 par value per share
("Common Stock") and certain warrants (the "Warrants") to acquire shares of
Common Stock (the shares acquired pursuant to the Purchase Agreement and
acquired upon exercise or in exchange for the Warrant in accordance with its
terms being collectively referred to herein as the "Shares"); and

     WHEREAS, the Company wishes to grant each of the Stockholders certain
registration rights upon and subject to the terms and conditions as set forth
herein;

     NOW, THEREFORE, in consideration of the mutual promises and covenants set
forth herein and in the Purchase Agreement, the parties hereby agree as follows:

     1.  Certain Definitions.  In addition to the other capitalized terms
         -------------------
defined throughout this Agreement, as used in this Agreement, the following
terms shall have the meanings set forth below:

     "Commission" shall mean the Securities and Exchange Commission or any other
federal agency at the time administering the Securities Act.

     "Registrable Securities" shall mean (i) the Shares and any and all shares
of Common Stock issued or issuable at any time or from time to time in respect
of which the Company has previously or may in the future grant in writing
registration rights and (ii) any Common Stock issued or issuable at any time or
from time to time in respect of the Shares or the Registrable Securities upon a
stock split, stock dividend, recapitalization or other similar event involving
the Company.

     The terms "register," "registered," and "registration" refer to a
registration effected by preparing and filing a registration statement in
compliance with the Securities Act, and the declaration or ordering by the
Commission of the effectiveness of such registration statement.

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     "Registration Expenses" shall mean all expenses, other than Selling
Expenses (as defined below), incurred by the Company in complying with Section 2
hereof, including, without limitation, all registration, qualification and
filing fees, exchange listing fees, printing expenses, escrow fees, fees and
disbursements of counsel for the Company, blue sky fees and expenses and the
expense of any special audits incident to or required by any such registration
(but excluding the compensation of regular employees of the Company which shall
be paid in any event by the Company).

     "S-3 Demand Registration" shall have the meaning ascribed to such term in
Section 2.1(e).

     "Securities Act" shall mean the Securities Act of 1933, as amended, or any
similar federal statute and the rules and regulations of the Commission
thereunder, all as the same shall be in effect at the time.

     "Selling Expenses" shall mean the underwriting discounts, selling
commissions and stock transfer taxes applicable to the securities registered by
a Stockholder and all fees and disbursements of counsel for such Stockholder.

     "Stockholders" shall mean the owners of Common Stock identified on the
signature page hereof, each of whom is referred to individually herein as a
"Stockholder" and a transferee of Registrable Securities from a Stockholder,
provided such transfer complies with Section 3.2 of this Agreement.

     "Underwritten Public Offering" shall mean a public offering in which Common
Stock is offered and sold on a firm commitment basis through one or more
underwriters, all pursuant to an underwriting agreement between the Company and
such underwriters.

     2.  Registration Rights.
         -------------------

         2.1  Demand Registration
              -------------------

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          (a)  Request for Registration.  Subject to the terms hereof, beginning
               ------------------------
     July 21, 1998, and at any time thereafter prior to January 21, 2003,
     Stockholders who collectively own a majority of the Registrable Securities
     then owned by the Stockholders may make a written request for registration
     under the Securities Act pursuant to this Section 2.1 of all or part of
     their Registrable Securities (a "Demand Registration").  Such request will
     specify the number of shares of Registrable Securities proposed to be sold
     (which, in any event, shall not be less than 1,000,000 shares in the
     aggregate) and will also specify the intended method of disposition
     thereof.  Upon receipt of such written request, the Company shall (i)
     promptly give written notice of the proposed registration to all other
     Stockholders; and (ii) as soon as practicable, use commercially reasonable
     efforts to effect such a registration statement in accordance with Section
     2.7 hereof, and will also include in such registration all Registrable
     Securities of other Stockholders with respect to which the Company has
     received written requests for inclusion therein within 20 days after their
     receipt of the Company's notice.  The Company shall be obligated to
     register Registerable Securities for the Purchasers pursuant to this
     Section 2.1 on one occasion only, unless solely because of the rights of
     the Existing Holders (as defined in Section 2.4) the Stockholders are not
     able to include 90% or more of the Registrable Securities they wish to
     include in such registration, in which case such registration shall not
     count under this Section 2.1.  If such a registration has become effective
     but is subsequently withdrawn by the Company (but not withdrawn by any
     Stockholder or as a result of any action or omission by any Stockholder)
     before completion of the offering contemplated thereby, then such
     registration shall not count as the Demand Registration contemplated by
     this Section 2.

          (b)  Underwritten Public Offering.  If a Demand Registration is in the
               ----------------------------
     form of an Underwritten Public Offering, the Company shall select the
     managing underwriter or underwriters for such offering subject to the
     approval of the Company (which approval shall not be unreasonably
     withheld), and the Company shall enter into an underwriting agreement with
     such underwriter containing representations, warranties, indemnities and
     agreements then customarily included by an issuer in underwriting
     agreements with respect to secondary distributions.  The Company shall not
     cause the registration under the Securities Act of any other shares of its
     Common Stock to become effective (other than any registration of stock
     under or interests in any benefit or compensation plan, or registration in
     connection with any acquisition, or pursuant to any Rule 145 or similar
     transaction) during the effectiveness of a registration requested hereunder
     for an Underwritten Public Offering if, in the judgment of the managing
     underwriter or managing underwriters, such registration would adversely
     affect the offering of the Registrable Securities subject to the Demand
     Registration.

          (c)  Inclusion of Additional Shares.  The Company may include in a
               ------------------------------
     registration pursuant to Section 2.1(b) additional securities for its own
     account or for the account of other third parties in amounts as determined
     by the Company's Board of Directors ("Additional Shares"), so long as the
     inclusion thereof does not in any way exclude or otherwise impair the
     rights of Stockholders who have requested registration pursuant to Section
     2.1(a) above to include in such registration all Registrable Securities so
     requested, subject only to the underwriters' market limitation specified in
     Section 2.3.

                                       3
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     Notwithstanding any other provision of this Section 2.1(c), if the lead
     underwriter managing the offering determines that, because of marketing
     factors, all of the Registrable Securities and Additional Shares requested
     to be registered may not be included in the offering, then all or a portion
     of the Additional Shares shall be excluded to the extent so required by
     such limitation, prior to the exclusion, if any, of Registrable Securities
     of the Stockholders. To facilitate the allocation of shares in accordance
     with the above provisions, the Company or the underwriters may round the
     number of shares allocated to any person to the nearest 100 shares.

          (d)  Expenses.  In any registration initiated as a Demand
               --------
     Registration, the Company will pay all Registration Expenses in connection
     therewith, whether or not it becomes effective.

          (e)  S-3 Demand Registration.  As an alternative to Section 2.1(b),
               -----------------------
     during the term of this Agreement, the Stockholders may make a written
     request for a selling stockholders' shelf registration on Form S-3 (or any
     equivalent or successor form under the Securities Act) pursuant to this
     Section 2.1(e) (an "S-3 Demand Registration") of all or part of the
     Stockholders' Registrable Securities. Such request will specify the number
     of shares of Registrable Securities proposed to be registered (which shall
     not in any event be less than 250,000 shares) and will also specify the
     intended method(s) of disposition thereof. The Company will pay all
     Registration Expenses in connection with any S-3 Demand Registration.

          2.2  Piggyback Registration.
               ----------------------

          (a)  Notice of Registration. Subject to the terms hereof, beginning
               ----------------------
     July 21, 1998, if at any time or from time to time thereafter prior to
     January 21, 2003 (except as otherwise provided in Section 2.7), the Company
     shall determine to register any of its Common Stock for its own account
     relating to an Underwritten Public Offering, the Company shall:

               (i)  promptly, but in any event at least 20 days before the
          Company files a registration statement for an Underwritten Public
          Offering, give to each Stockholder written notice thereof; and

               (ii) include in such registration (and any related qualification
          under blue sky laws or other compliance), and in the underwriting
          involved therein, such Registrable Securities as each Stockholder may
          request in a writing delivered to the Company within 10 days after
          each Stockholder's receipt of the Company's written notice delivered
          pursuant to Section 2.1(a)(i) above.

          (b)  Right to Terminate Registration. The Company shall have the right
               -------------------------------
     to terminate or withdraw any registration initiated by it under this
     Section 2.2 prior to the effectiveness of such registration whether or not
     any Stockholder has elected to include its Registrable Securities in such
     registration, provided, however, that in such event, the Company shall
     promptly pay all reasonable out-of-pocket costs and expenses of the

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     Stockholders (including, without limitation, all reasonable fees and
     disbursements of one law firm chosen to represent the Stockholders)
     incurred in connection with such terminated registration.

          2.3  Underwriting.  The right of each Stockholder to registration
               ------------
pursuant to Section 2.2 shall be conditioned upon such Stockholder's
participation in such underwriting, and the inclusion of Registrable Securities
in the underwriting shall be limited to the extent provided herein. Each
Stockholder, and all other stockholders proposing to distribute their securities
through such underwriting (in the case of Section 2.2 hereof) shall (together
with the Company) enter into an underwriting agreement in customary form with
the managing underwriter(s) selected for such underwriting by the Company.
Subject to the provisions of Section 2.4 below, if the managing underwriter(s)
determine that marketing factors require a limitation of the number of shares of
the selling stockholders to be underwritten, the managing underwriter(s) may
limit some or all of the Registrable Securities that may be included in the
registration and underwriting as follows: the number of Registrable Securities
that may be included in the registration and underwriting by each Stockholder
shall be determined by multiplying the number of shares of Registrable
Securities of all selling stockholders of the Company which the managing
underwriter(s) are willing to include in such registration and underwriting,
times a fraction, the numerator of which is the number of Registrable Securities
requested to be included in such registration and underwriting by each
Stockholder, and the denominator of which is the total number of Registrable
Securities which all selling stockholders of the Company have requested to have
included in such registration and underwriting.  To facilitate the allocation of
shares in accordance with the above provisions, the Company may round the number
of shares allocable to any such person to the nearest 100 shares. If any
Stockholder disapproves of the terms of any such underwriting, it may elect to
withdraw therefrom by written notice to the Company and the managing
underwriter(s), delivered not less than seven days before the effective date.

          2.4  Subordination of Registration Rights.
               ------------------------------------

     (a)  Until September 30, 1998, in the event that the managing
underwriter(s) of any underwriting shall inform the Company of its intention to
limit the number of Registrable Securities to be included in any registration
and underwriting pursuant to Section 2.3 above, all Registrable Securities held
by Don V. Ingram, a resident of Dallas County, Texas, and PTX Partners, a Texas
limited partnership (collectively, the "Existing Holders") who have notified the
Company of their intent to include their Registrable Securities in such
registration and underwriting pursuant to Section 2.2 above, shall be included
in such registration and underwriting (subject to the terms of that certain
Amended and Restated Registration Agreement dated September 30, 1988, as amended
(the "1988 Agreement")), before the Stockholders shall be permitted to include
any of their Registrable Securities in such registration and underwriting. In
the event that additional Registrable Securities are available for inclusion in
such registration and underwriting after the inclusion of the Existing Holders'
Registrable Securities, then the number of Registrable Securities to be included
in such registration and underwriting by the Stockholders shall be determined by
multiplying the number of shares of Registrable Securities remaining after the
inclusion of the Existing Holders' Registrable Securities which the managing
underwriter is willing to include in such registration and

                                       5
<PAGE>

underwriting, times a fraction, the numerator of which is the number of
Registrable Securities requested to be included in such registration and
underwriting by each Stockholder, and the denominator of which is the total
number of Registrable Securities which all selling stockholders of the Company
have requested to have included in such registration and underwriting.

     (b)  The Company hereby agrees that if the Company, after the date hereof,
grants to any person rights to register the Company's Common Stock under the
Securities Act of 1933, as amended, ("Registration Rights") that provide for
terms that are in any manner more favorable to the holder of such Registration
Rights than the equivalent terms of this Agreement then in effect (or if the
Company amends or waives any provision of any Registration Rights existing on
the date hereof to provide for terms that are more favorable to the holder
thereof than the equivalent terms of this Agreement), then the Company shall
amend this Agreement to provide for any (or all) of such more favorable terms as
Purchaser shall elect to include herein.

          2.5  No Other Registration Rights.  Except for (i) the rights granted
               ----------------------------
pursuant to the 1988 Agreement, (ii) the rights granted pursuant to the
Registration Rights Agreement dated as of January 21, 1997, among the Company
and the former stockholders of Rock Creek Aluminum, Inc., (iii) the rights
granted pursuant to the Registration Rights Agreement dated as of November 4,
1997, among the Company and the former shareholders of Alchem Aluminum, Inc. and
(iv) the rights granted pursuant to this Agreement, the Company is not a party
to, nor is it bound by any agreement with respect to its capital stock which
grants registration rights to any person or entity.

          2.6  Expenses of Registration.  All Registration Expenses incurred in
               ------------------------
connection with all registrations pursuant to Sections 2.1 and 2.2 shall be
borne by the Company. Unless otherwise stated herein, all Selling Expenses
relating to securities registered on behalf of any Stockholder shall be borne by
such Stockholder in proportion to such Stockholder's percentage ownership of all
selling Stockholders' Registrable Securities being registered.

          2.7  Registration Procedures.  Whenever the Stockholders have
               -----------------------
requested that any Registrable Securities be registered pursuant to this
Agreement, the Company will use its reasonable best efforts to effect the
registration and the sale of such Registrable Securities under the Securities
Act, as provided herein, and as expeditiously as possible:

          (a)  prepare and file with the Securities and Exchange Commission (the
     "Commission") as soon as practicable but in no event later than ninety (90)
     days after receipt of a request to file a registration statement with
     respect to Registrable Securities, a registration statement on any form for
     which the Company then qualifies and which counsel for the Company shall
     deem appropriate and which form shall be available for the sale of such
     issue of Registrable Securities in accordance with the intended method of
     distribution thereof, and use its best efforts to cause such registration
     statement to become effective as promptly as practicable thereafter;
     provided, that if the Company shall furnish to the Holders a certificate
     --------
     signed by the Chief Executive Officer of the Company stating that in the
     good faith reasonable judgment of the Board of Directors it would be
     significantly disadvantageous to the Company and its stockholders for such
     a registration statement to be filed on or before the date filing would be
     required or to

                                       6
<PAGE>

     become effective, the Company shall have an additional period of not more
     than one hundred eighty (180) days within which to file (or before which it
     requests the effectiveness of) such registration statement; and provided,
                                                                     --------
     further, that before filing a registration statement or prospectus or any
     -------
     amendments or supplements thereto, the Company will (i) furnish to counsel
     selected by the Stockholders copies of all such documents proposed to be
     filed and (ii) notify each seller of Registrable Securities of any stop
     order issued or threatened by the Commission and take all actions required
     to prevent the entry of such stop order or to remove it if entered;

          (b) prepare and file with the Commission such amendments and
     supplements to such registration statement and the prospectus used in
     connection therewith as may be necessary to keep such registration
     statement effective for a period of not less than 90 days or such shorter
     period which will terminate when all Registrable Securities covered by such
     registration statement have been sold, and comply with the provisions of
     the Securities Act with respect to the disposition of all securities
     covered by such registration statement during such period in accordance
     with the intended methods of disposition by the sellers thereof set forth
     in such registration statement;

          (c) furnish to each seller of Registrable Securities to be included in
     a registration statement copies of such registration statement as filed and
     each amendment and supplement thereto (in each case including all exhibits
     thereto), the prospectus included in such registration statement (including
     each preliminary prospectus) and such other documents as such seller may
     reasonably request in order to facilitate the disposition of the
     Registrable Securities owned by such seller;

          (d) use its reasonable best efforts to register or qualify such
     Registrable Securities under such other securities or blue sky laws of such
     jurisdictions as any seller reasonably requests and do any and all other
     acts and things which may be necessary or advisable to enable such seller
     to consummate the disposition in such jurisdictions of the Registrable
     Securities owned by such seller; provided, that the Company will not be
                                      --------
     required to (i) qualify generally to transact business in any jurisdiction
     where it would not otherwise be required to qualify but for this Section
     2.7(d), (ii) subject itself to taxation in any such jurisdiction where it
     would not otherwise be subject to taxation or (iii) consent to general
     service of process in any such jurisdiction, but the Company will be
     required to consent to service of process in actions arising out of or in
     connection with the sale of the Registrable Securities or any violation of
     state securities laws;

          (e) use its reasonable best efforts to cause the Registrable
     Securities covered by such registration statement to be registered with or
     approved by any other governmental agencies or authorities as may be
     necessary by virtue of the business and operations of the Company to enable
     the seller or sellers thereof to consummate the disposition of such
     Registrable Securities;

          (f) notify each seller of such Registrable Securities at any time when
     a prospectus relating thereto is required to be delivered under the
     Securities Act, of the happening of any event as a result of which the
     prospectus included in such registration

                                       7
<PAGE>

     statement contains an untrue statement of a material fact or omits to state
     any material fact required to be stated therein or necessary to make the
     statements therein not misleading, and the Company will prepare a
     supplement or amendment to such prospectus so that, as thereafter delivered
     to the purchaser of such Registrable Securities, such prospectus will not
     contain an untrue statement of a material fact or omit to state any
     material fact required to be stated therein or necessary to make the
     statements therein, in light of the circumstances under which they were
     made, not misleading;

          (g) enter into customary agreements (including an underwriting
     agreement in customary form) and take such other actions as are required in
     order to expedite or facilitate the disposition of such Registrable
     Securities;

          (h) otherwise comply with all applicable rules and regulations of the
     Commission; and

          (i) cause all such Registrable Securities to be listed on each
     securities exchange on which similar securities issued by the Company are
     then listed, provided that the applicable listing requirements are
     satisfied.

          The Company may require each seller of Registrable Securities as to
which any registration is being effected to furnish to the Company such
information regarding matters relating to such seller's Registrable Securities
as are customary and as the Company may from time to time reasonably request in
writing.

          Each seller of Registrable Securities agrees that, upon receipt of any
notice from the Company of the happening of any event of the kind described in
Section 2.7(f) hereof, the seller will forthwith discontinue disposition of
Registrable Securities pursuant to the registration statement covering such
Registrable Securities until such seller's receipt of the copies of the
supplemented or amended prospectus contemplated by Section 2.7(f) hereof, and,
if so directed by the Company, such seller will deliver to the Company (at the
Company's expense) all copies, other than permanent file copies then in such
seller's possession, of the prospectus covering such Registrable Securities
current at the time of receipt of such notice.  In the event the Company shall
give any such notice, the Company shall extend the period during which such
registration statement shall be maintained effective pursuant to this Agreement
(including the period referred to in Section 2.7(b)) by the number of days
during the period from and including the date of the giving of such notice
pursuant to Section 2.7(f) hereof to and including the date when each seller of
Registrable Securities covered by such registration statement shall have
received the copies of the supplemented or amended prospectus contemplated by
Section 2.7(f) hereof.

                                       8
<PAGE>

          2.8  Preparation; Reasonable Investigation.  In connection with the
               -------------------------------------
preparation and filing of each registration statement under the Securities Act
pursuant to this Agreement, the Company will give each seller of Registrable
Securities, their underwriters, if any, and their respective counsel, the
opportunity to participate in the preparation of such registration statement,
each prospectus included therein or filed with the Commission, and each
amendment thereof or supplement thereto, and will give each of them such access
to its books and records and such opportunities to discuss the business of the
Company with its officers and the independent public accountants who have
certified its financial statements as shall be necessary to conduct a reasonable
investigation within the meaning of the Securities Act.

          2.9  Indemnification; Contribution.
               -----------------------------

          (a)  Indemnification by the Company.  The Company agrees to indemnify,
               ------------------------------
     to the full extent permitted by law, each seller of Registrable Securities,
     its officers, directors, trustees, partners and agents and each Person who
     controls such seller (within the meaning of the Securities Act) against all
     losses, claims, damages, liabilities and expenses ("Losses") caused by any
     untrue or alleged untrue statement of material fact contained in any
     registration statement, prospectus or preliminary prospectus or any
     omission or alleged omission to state therein a material fact required to
     be stated therein or necessary to make the statements therein (in case of a
     prospectus or preliminary prospectus, in light of the circumstances under
     which they were made) not misleading; provided, however, that the Company
                                           --------  -------
     will not be liable to the extent that such Losses arise from and are based
     on an untrue statement or omission or alleged untrue statement or omission
     of a material fact in a registration statement or prospectus which is made
     in reliance on and in conformity with written information furnished to the
     Company in an instrument duly executed by or on behalf of such seller.

          (b)  Indemnification by Seller of Registrable Securities.  In
               ---------------------------------------------------
     connection with any registration statement in which a seller of Registrable
     Securities is participating, each such seller will furnish to the Company
     in writing such information with respect to such seller as the Company
     reasonably requests for use in connection with any such registration
     statement or prospectus and agrees to indemnify, to the full extent
     permitted by law, the Company, its directors and officers and each Person
     who controls the Company (within the meaning of the Securities Act) against
     any Losses resulting from any untrue or alleged untrue statement of a
     material fact or any omission or alleged omission of a material fact
     required to be stated in the registration statement, prospectus or
     preliminary prospectus or any amendment thereof or supplement thereto or
     necessary to make the statements therein (in the case of a prospectus or
     preliminary prospectus, in the light of the circumstances under which they
     were made) not misleading, to the extent, but only to the extent, that such
     Losses arise from and are based on an untrue statement or omission or
     alleged untrue statement or omission of a material fact in a registration
     statement or prospectus which is made in reliance on and in conformity with
     written information furnished to the Company in an instrument duly executed
     by or on behalf of such seller.  In no event shall a seller of Registrable
     Securities be required to contribute any amount under this Section 2.9 in
     excess of the lesser of (i) that proportion

                                       9
<PAGE>

     of the total of such Losses indemnified against equal to the proportion of
     the total securities sold under such registration statement which is being
     sold by such seller or (ii) the net proceeds received by such seller from
     its sale of securities under such registration statement.

          (c) Conduct of Indemnification Proceedings.  Promptly after the
              --------------------------------------
     receipt by an indemnified party of a notice of any claim, action, suit or
     proceeding of any third party which is subject to indemnification
     hereunder, such party (the "Indemnified Party") shall give written notice
     of such claim to the party obligated to provide indemnification hereunder
     (the "Indemnifying Party"), stating the nature and basis of such claim and
     the amount thereof, to the extent known.  Failure of the Indemnified Party
     to give such notice promptly shall not relieve the Indemnifying Party from
     any liability which it may have on account of this indemnification or
     otherwise, except to the extent that the Indemnifying Party is materially
     prejudiced thereby (except that the Indemnifying Party shall not be liable
     for any expenses incurred during the period in which the Indemnified Party
     failed to give such notice).  The Indemnifying Party shall be entitled to
     participate in the defense of and, if it so chooses, to assume the defense
     of, or otherwise contest, such claim, action, suit or proceeding with
     counsel selected by the Indemnifying Party and reasonably satisfactory to
     the Indemnified Party; provided, that, the Indemnified Party shall be
                            --------
     entitled, to the extent it so elects and at its sole cost and expense, to
     assume and control the defense of any claim involving any equitable claim,
     including, but not limited to, injunctive relief.  Upon the election by the
     Indemnifying Party to assume the defense of, or otherwise contest, such
     claim, action, suit or proceeding, the Indemnifying Party shall not be
     liable for any legal or other expenses subsequently incurred by the
     Indemnified Party in connection with the defense thereof, although the
     Indemnified Party shall have the right to participate in the defense
     thereof and to employ counsel, at its own expense.  Notwithstanding the
     foregoing, the Indemnifying Party shall be liable for the reasonable fees
     and expenses of counsel employed by the Indemnified Party, if, and only to
     the extent that (i) the Indemnifying Party has not employed counsel or
     counsel reasonably acceptable to the Indemnified Party to assume the
     defense of such action within a reasonable time after receiving notice of
     the commencement of the action, (ii) the employment of counsel and the
     amount reimbursable therefor by the Indemnified Party has been authorized
     in writing by the Indemnifying Party or (iii) representation of the
     Indemnifying Party and the Indemnified Party by the same counsel would, in
     the reasonable determination of such Indemnified Party, constitute a
     conflict of interest (in which case the Indemnifying Party will not have
     the right to direct the defense of such action on behalf of the Indemnified
     Party).  The parties shall use commercially reasonable efforts to minimize
     Losses from claims by third parties and shall act in good faith in
     responding to, defending against, settling or otherwise dealing with such
     claims, notwithstanding any dispute as to liability as between the parties
     under this Section 2.9.  The parties shall also cooperate in any such
     defense, give each other reasonable access to all information relevant
     thereto and make employees and other representatives available on a
     mutually convenient basis to provide additional information and explanation
     of any material provided in connection therewith.  Whether or not the
     Indemnifying Party shall have assumed the defense, the Indemnifying Party
     shall not be obligated to indemnify the other party hereunder for any
     settlement entered

                                       10
<PAGE>

     into without the Indemnifying Party's prior written consent, which consent
     shall not be unreasonably withheld or delayed.

          (d)  Contribution. If the indemnification provided for in this Section
               ------------
     2.9 is for any reason held by a court of competent jurisdiction to be
     unavailable to an  Indemnified Party in respect of any Losses referred to
     therein, then the Indemnifying Party, in lieu of indemnifying such
     Indemnified Party thereunder, shall contribute to the amount paid or
     payable by such Indemnified Party as a result of such Losses (i) in such
     proportion as is appropriate to reflect the relative benefits received by
     the Indemnifying Party and the Indemnified Party, or (ii) if the allocation
     provided by clause (i) above is not permitted by applicable law, in such
     proportion as is appropriate to reflect not only the relative benefits
     referred to in clause (i) above but also the relative fault of the
     Indemnifying Party and the Indemnified Party in connection with the action
     or inaction which resulted in such Losses, as well as any other relevant
     equitable considerations.  In connection with any registration of the
     Company's securities, the relative benefits received by the Indemnifying
     Party and the Indemnified Party shall be deemed to be in the same
     respective proportions that the net proceeds from the offering (before
     deducting expenses) received by the Indemnifying Party and the Indemnified
     Party, in each case as set forth in the table on the cover page of the
     applicable prospectus, bear to the aggregate public offering price of the
     securities so offered.  The relative fault of the Indemnifying Party and
     the Indemnified Party shall be determined by reference to, among other
     things, whether the untrue or alleged untrue statement of a material fact
     or the omission or alleged omission to state a material fact relates to
     information supplied by the Indemnifying Party or the Indemnified Party and
     the parties' relative intent, knowledge, access to information and
     opportunity to correct or prevent such statement or omission.

          The Indemnifying Party and the Indemnified Party agree that it would
not be just and equitable if contribution pursuant to the foregoing paragraph
were determined by pro rata or per capita allocation or by any other method of
allocation which does not take account of the equitable considerations referred
to in the immediately preceding paragraph.  In connection with any registration
of the Company's securities, in no event shall a seller of Registrable
Securities be required to contribute any amount under this Section 2.9 in excess
of the lesser of (i) that proportion of the total of such Losses indemnified
against equal to the proportion of the total securities sold under such
registration statement which is being sold by such seller or (ii) the net
proceeds received by such seller from its sale of securities under such
registration statement.  No person found guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not found guilty of such fraudulent
misrepresentation.

          2.10 Participation in Underwritten Registrations.  No Person may
               -------------------------------------------
participate in any underwritten registration hereunder unless such Person (a)
agrees to sell such Person's securities on the basis provided in any
underwriting arrangements approved by the Persons entitled hereunder to approve
such arrangements and (b) completes and executes all questionnaires, powers of
attorney, indemnities, underwriting agreements and other documents reasonably
required under the terms of such underwriting arrangements.

                                       11
<PAGE>

          2.11 Certain Information.  Each Stockholder agrees, with respect to
               -------------------
any Registrable Securities included in any registration, to furnish to the
Company such information regarding such Stockholder, the Registrable Securities
and the distribution proposed by such Stockholder as the Company may reasonably
request in writing and as shall be required in connection with any registration,
qualification or compliance referred to in Sections 2.1 or 2.2.

          2.12 Rule 144 Reporting. With a view to making available the benefits
               ------------------
of certain rules and regulations of the Commission which may at any time permit
the sale of the Restricted Securities (such term being used herein as defined in
Rule 144 promulgated under the Securities Act) to the public without
registration, the Company agrees to:

          (a)  Make and keep public information available, as those terms are
     understood and defined in Rule 144 under the Securities Act, at all times
     during which the Company is subject to the reporting requirements of the
     Securities Exchange Act of 1934, as amended (the "Exchange Act");

          (b)  File with the Commission in a timely manner all reports and other
     documents required of the Company under the Securities Act and the Exchange
     Act (at all times during which the Company is subject to such reporting
     requirements); and

          (c)  So long as any Stockholder owns any Restricted Securities, to
     furnish to such Stockholder forthwith upon request a written statement by
     the Company as to its compliance with the reporting requirements of said
     Rule 144 and with regard to the Securities Act and the Exchange Act (at all
     times during which the Company is subject to such reporting requirements),
     a copy of the most recent annual or quarterly report of the Company, and
     such other non-confidential reports and documents of the Company and other
     non-confidential information in the possession of or reasonably obtainable
     by the Company as such Stockholder may reasonably request in availing
     himself of any rule or regulation of the Commission allowing Stockholder to
     sell any such securities without registration.

          2.13 Holdback Agreements.  Each Stockholder agrees not to effect any
               -------------------
public sale or distribution of the issue being registered or a similar security
of the Company, or any securities convertible into or exchangeable or
exercisable for such securities, during the 30 days prior to, and during the 90-
day period beginning on, the effective date of such registration statement
(except as part of such registration), unless the Company in the case of a non-
Underwritten Public Offering, or the managing underwriter(s) in the case of an
Underwritten Public Offering, otherwise agree or consent in writing.

     3.   Miscellaneous.
          -------------

          3.1  Governing Law. This Agreement shall be governed in all respects
               -------------
by the laws of the State of Texas.

                                       12
<PAGE>

          3.2  No Transfer; Termination.  The registration rights contemplated
               ------------------------
herein are not transferable, except (i) by operation of law and by the laws of
descent and distribution, (ii) to any member of a Stockholder's immediate
family, (iii) to any beneficiaries of any Stockholder which is a trust or
foundation, or (iv) to any trust, partnership or other entity as to which all of
the beneficiaries or partners consist of a Stockholder or members of such
Stockholder's immediate family. The registration rights granted herein shall
terminate, and the registration rights will not be exercisable by any
Stockholder (or such Stockholder's lawful assigns or transferees pursuant to
this Section 3.2) after said termination date, on January 21, 2003.

          3.3  Entire Agreement; Amendment. This Agreement constitutes the full
               ---------------------------
and entire understanding and agreement between the parties with regard to the
subject matter hereof. This Agreement, or any provision hereof, may be amended,
waived, discharged or terminated only upon the written consent of the Company
and those Stockholders who are the record holders of at least a majority of the
Shares issued pursuant to the Purchase Agreement.

          3.4  Notices.   All notices or other communications which are required
               -------
or may be given under this Agreement shall be in writing and shall be deemed to
have been duly given when delivered in person, transmitted by telecopier or
mailed by registered or certified first class mail, postage prepaid, return
receipt requested to the parties hereto at the address set forth below (as the
same may be changed from time to time by notice similarly given) or the last
known business or residence address of such other person as may be designated by
either party hereto in writing.

          Stockholders:

               c/o Mr. M. Russ Robinson
               U.S. Zinc Corporation
               6020 Navigation St.
               Houston, TX 77001
               Facsimile No.: (713) 923-1783

          Company:

               Mr. Don V. Ingram
               IMCO Recycling Inc.
               5215 North O'Connor Blvd.
               Irving, Texas 75039
               Facsimile No.: (972) 401-7342

          3.5  Delays or Omissions. Except as expressly provided herein, no
               -------------------
delay or omission to exercise any right, power or remedy accruing to any party
to this Agreement shall

                                       13
<PAGE>

impair any such right, power or remedy of such party nor shall it be construed
to be a waiver of any such breach or default, or an acquiescence therein, or of
or in any similar breach or default thereafter occurring; nor shall any waiver
of any single breach or default be deemed a waiver of any other breach or
default theretofore or thereafter occurring. Any waiver, permit, consent or
approval of any kind or character on the part of any party of any breach or
default under this Agreement, or any waiver on the part of any party of any
provisions or conditions of this agreement, must be in writing and shall be
effective only to the extent specifically set forth in such writing. All
remedies, either under this Agreement or by law or otherwise afforded to any
party to this Agreement, shall be cumulative and not alternative.

          3.6  Counterparts. This Agreement may be executed in any number of
               ------------
counterparts, each of which shall be enforceable against the parties actually
executing such counterparts, and all of which together shall constitute one
instrument.

          3.7  Severability. In the event that any provision of this Agreement
               ------------
becomes or is declared by a court of competent jurisdiction to be illegal,
unenforceable or void, this Agreement shall continue in full force and effect
without said provision.

          3.8  Titles and Subtitles. The titles and subtitles used in this
               --------------------
Agreement are used for convenience only and are not considered in construing or
interpreting this Agreement.

          3.9  Construction.  Whenever the context requires, the gender of all
               ------------
words used in this Agreement shall include the masculine, feminine, and neuter,
and the number of all words shall include the singular and the plural.

                           [Signature page follows]

                                       14
<PAGE>

     IN WITNESS WHEREOF, the undersigned or each of their respective duly
authorized officers or representatives have executed this agreement effective
upon the date first set forth above.

                                        COMPANY:

                                        IMCO RECYCLING INC.

                                        By: ____________________________________
                                        Title: _________________________________

                                        STOCKHOLDERS:

                                        THE MINNETTE AND JEROME ROBINSON
                                        COMMUNITY PROPERTY TRUST

                                        By: ____________________________________
                                                Jerome Robinson, Trustee

                                        By: ____________________________________
                                                Minnette Robinson, Trustee

                                        KANALY TRUST COMPANY, Co-Trustee (in its
                                        fiduciary capacity as Co-Trustee and not
                                        otherwise)

                                        By: ____________________________________
                                                Joan L. Romans, Sr. Vice
                                        President and Trust Officer

                                        THE MINNETTE AND JEROME ROBINSON
                                        FOUNDATION

                                        By: ____________________________________
                                            Dvosha G. Roscoe, Vice President

                                       15
<PAGE>

                                        THE MINNETTE AND JEROME ROBINSON
                                        CHARITABLE REMAINDER TRUST

                                        KANALY TRUST COMPANY, Trustee (in its
                                        fiduciary capicity as sole Trustee and
                                        not otherwise)

                                        By: ____________________________________
                                                Joan L. Romans, Sr. Vice
                                        President and Trust Officer

                                        ________________________________________
                                        M. RUSS ROBINSON

                                        ________________________________________
                                        HOWARD ROBINSON

                                        ________________________________________
                                        MINDY ROBINSON BROWN

                                       16

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