<PAGE>


                                                                   EXHIBIT 10.13

               THIRD AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT


         THIS THIRD AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT (the
"Third Amendment"), dated as of August 15, 2000, is between INDUSTRIAL HOLDINGS,
INC. ("Borrower"), and COMERICA BANK-TEXAS ("Agent").

                                    RECITALS:

         A.       Borrower Banks and  Agent have entered into that certain
Amended and Restated Credit Agreement (the "Agreement") dated as of June 17,
1999.

         B.       Pursuant to the Agreement, Guarantors executed that certain
Amended and Restated Guaranty Agreement (the "Guaranty") dated as of June 17,
1999 which guaranteed to Agent the payment and performance of the Obligations.

         C.       Borrower, Banks and Agent have previously amended the
Agreement and now desire to amend the Agreement a third time as herein set
forth,

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

                                    ARTICLE I

                                   DEFINITIONS

         1.1 DEFINITIONS. Capitalized terms used in this Third Amendment, to the
extent not otherwise defined herein, shall have the same meanings as in the
Agreement, as amended hereby.

                                   ARTICLE II

                                   AMENDMENTS

         2.1 AMENDMENT TO ARTICLE II. Section 2.8 is hereby amended by adding a
new section (d) thereto to read as follows:

                  (d) In return for the Banks' agreeing to enter into the Third
                  Amendment, the Borrower agrees to pay a fee in the amount of
                  FIFTY THOUSAND AND NO/100 DOLLARS ($50,000.00). TWENTY-FIVE
                  THOUSAND AND NO/100 DOLLARS ($25,000.00) of the fee is payable
                  contemporaneous with the execution of this Third Amendment.
                  The remaining TWENTY-FIVE THOUSAND AND NO/100 DOLLARS
                  ($25,000.00) shall be due and payable on September 22, 2000.
                  In the event that, as of the close of business on September
                  22, 2000, the Borrower has complied with the requirements of
                  both Subsections 11.1(p) and 11.1(v) hereof, then the Banks
                  shall not be entitled to enforce payment of the remaining
                  TWENTY-FIVE THOUSAND AND NO/100 DOLLARS ($25,000.00) fee and
                  the Borrower shall be relieved of its obligation to pay that
                  remaining portion of the fee.

         2.2 AMENDMENT TO ARTICLE X. Section 10.11, which was added to the
Agreement by the Second Amendment, is hereby revised by deleting the Section
10.11 in its entirety and replacing it with the following:

                  Section 10.11 EXPENDITURES. The Borrower shall not make or
         incur, and will not permit any Subsidiary to make or incur, Capital
         Expenditures, including Capital Lease Obligations, in excess of
         $5,500,000.00 for the calendar year 2000. In calculating Capital


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         Expenditures, the Borrower shall not include Capital Expenditures made
         by its subsidiary, Blastco Services Company.

         2.3 AMENDMENT TO ARTICLE XI. The following Subsections of Article XI
are hereby amended by deleting the current provisions, which were added by the
Second Amendment to the Agreement, in their entirety and replacing them with the
following:

                  Section 11.1(p). Should the Borrower fail to obtain prior to
         October 23, 2000 new equity and/or debt in a form and substance
         acceptable to the Banks and its debt subordinate in a fashion
         acceptable to Banks, in the aggregate principal amount of ONE MILLION
         FIVE HUNDRED THOUSAND AND NO/100 DOLLARS ($1,500,000.00).

                  Section 11.1(v). Should the Borrower fail to obtain by October
         23, 2000 a default waiver from Heller Financial, Inc., in form and
         substance acceptable to the Banks, waiving all of the current defaults
         by the Borrower to Heller Financial, Inc.

                                   ARTICLE III

                              CONDITIONS PRECEDENT

         3.1 CONDITIONS. The effectiveness of this Third Amendment is subject to
the satisfaction of the following conditions precedent:

         (a) Agent shall have received all of the following, each dated (unless
     otherwise indicated) the date of this Third Amendment, in form and
     substance satisfactory to Agent:

                           (1) RESOLUTIONS. Resolutions of the Board of
                  Directors of Borrower certified by its Secretary or an
                  Assistant Secretary which authorize the execution, delivery,
                  and performance by Borrower and each Guarantor of this
                  Amendment and the other Loan Documents to which Borrower and
                  each Guarantor is or is to be a party hereunder;

                           (2) INCUMBENCY CERTIFICATE. A certificate of
                  incumbency certified by the Secretary or an Assistant
                  Secretary of Borrower and each Guarantor certifying the names
                  of the officers of Borrower and each Guarantor authorized to
                  sign this Amendment and each of the other Loan Documents to
                  which Borrower and each Guarantor is or is to be a party
                  hereunder (including the certificates contemplated herein)
                  together with specimen signatures of such officers;

                           (3) BYLAWS. The bylaws of Borrower certified by the
                  Secretary or an Assistant Secretary of Borrower;

                           (4) GOVERNMENTAL CERTIFICATES. Certificates of the
                  appropriate government officials of the state of incorporation
                  of Borrower and each Guarantor as to the existence and good
                  standing of Borrower and each Guarantor, each dated within ten
                  (10) days prior to the date of this Third Amendment; and

                           (5) ADDITIONAL INFORMATION. Agent shall have received
                  such additional documents, instruments and information as
                  Agent or its legal counsel, Winstead Sechrest & Minick P.C.,
                  may request.

         (b) The representations and warranties contained herein and in all
     other Loan Documents, as amended hereby, shall be true and correct as of
     the date hereof as if made on the date hereof;

         (c) Except for as described on Exhibit "A" hereto no Event of Default
     shall have occurred and be continuing and no event or condition shall have
     occurred that with the giving of notice or lapse of time or


                                      EX-22
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     both would be an Event of Default.

         (d) All corporate proceedings taken in connection with the transactions
     contemplated by this Amendment and all documents, instruments, and other
     legal matters incident thereto shall be satisfactory to Agent and its legal
     counsel, Winstead Sechrest & Minick P.C.

         (e) The Borrower shall have reimbursed the Agent for fees and expenses
     paid or the fees and expenses of the Agent incurred, in connection with the
     Second Amendment to the Agreement and this Third Amendment to the Agreement
     including, but not limited to, the fees and expenses of the Agent's
     counsel.

                                   ARTICLE IV

                  RATIFICATIONS, REPRESENTATIONS AND WARRANTIES

         4.1 RATIFICATIONS. The terms and provisions set forth in this Third
Amendment shall modify and supersede all inconsistent terms and provisions set
forth in the Agreement and except as expressly modified and superseded by this
Amendment, the terms and provisions of the Agreement are ratified and confirmed
and shall continue in full force and effect. Borrower and Agent agree that the
Agreement as amended hereby shall continue to be legal, valid, binding and
enforceable in accordance with its terms.

         4.2 REPRESENTATIONS AND WARRANTIES. Borrower hereby represents and
warrants to Agent that (i) the execution, delivery and performance of this Third
Amendment and any and all other Loan Documents executed and/or delivered in
connection herewith have been authorized by all requisite corporate action on
the part of Borrower and will not violate the articles of incorporation or
bylaws of Borrower, (ii) the representations and warranties contained in the
Agreement, as amended hereby, and any other Loan Document are true and correct
on and as of the date hereof as though made on and as of the date hereof, (iii)
no Event of Default, other than those listed on Exhibit "A", has occurred and is
continuing and no event or condition has occurred that with the giving of notice
or lapse of time or both would be an Event of Default, and (iv) other than as
set forth on Exhibit "A", Borrower is in full compliance with all covenants and
agreements contained in the Agreement as amended hereby.

                                    ARTICLE V

         5.1 SWING LINE. The Banks acknowledge that certain disagreements have
existed over the Agent's operation of the Swing Line. The Banks further
acknowledge and agree that those disagreements are hereby resolved and all
claims relating to the Agent's prior operation of the Swing Line are hereby
released.

                                   ARTICLE VI

                                  MISCELLANEOUS

         6.1 SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations and
warranties made in this Third Amendment or any other Loan Document including any
Loan Document furnished in connection with this Amendment shall survive the
execution and delivery of this Amendment and the other Loan Documents, and no
investigation by any Bank or any closing shall affect the representations and
warranties or the right of Banks to rely upon them.

         6.2 REFERENCE TO AGREEMENT. Each of the Loan Documents, including the
Agreement and any and all other agreements, documents, or instruments now or
hereafter executed and delivered pursuant to the terms hereof or pursuant to the
terms of the Agreement as amended hereby, are hereby amended so that any
reference in such Loan Documents to the Agreement shall mean a reference to the
Agreement as amended hereby.

         6.3 EXPENSES OF AGENT. As provided in the Agreement, Borrower agrees to
pay on demand all costs and expenses incurred by Agent in connection with the
preparation, negotiation, and execution of this Third Amendment and the other
Loan Documents executed pursuant hereto and any and all amendments,


                                      EX-23
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modifications, and supplements thereto, including without limitation the costs
and fees of Agent's legal counsel, and all costs and expenses incurred by Agent
in connection with the enforcement or preservation of any rights under the
Agreement, as amended hereby, or any other Loan Document, including without
limitation the costs and fees of Agent's legal counsel.

         6.4  SEVERABILITY. Any provision of this Third Amendment held by a
court of competent jurisdiction to be invalid or unenforceable shall not impair
or invalidate the remainder of this Third Amendment and the effect thereof
shall be confined to the provision so held to be invalid or unenforceable.

         6.5  APPLICABLE LAW. This Third Amendment and all other Loan Documents
executed pursuant hereto shall be deemed to have been made and to be performable
in Dallas, Dallas County, Texas and shall be governed by and construed in
accordance with the laws of the State of Texas.

         6.6  SUCCESSORS AND ASSIGNS. This Third Amendment is binding upon and
shall inure to the benefit of the Banks and Borrower and their respective
successors and assigns, except Borrower may not assign or transfer any of its
rights or obligations hereunder without the prior written consent of the Banks.

         6.7  COUNTERPARTS. This Third Amendment may be executed in one or more
counterparts, each of which when so executed shall be deemed to be an original,
but all of which when taken together shall constitute one and the same
instrument.

         6.8  EFFECT OF WAIVER. No consent or waiver, express or implied, by the
Banks to or for any breach of or deviation from any covenant, condition or duty
by Borrower or Guarantor shall be deemed a consent or waiver to or of any other
breach of the same or any other covenant, condition or duty.

         6.9  HEADINGS. The headings, captions, and arrangements used in this
Third Amendment are for convenience only and shall not affect the interpretation
of this Third Amendment.

         6.10 NON-APPLICATION OF CHAPTER 346 OF TEXAS FINANCE CODE. The
provisions of Chapter 346 of the Texas Finance Code are specifically declared by
the parties hereto not to be applicable to this Third Amendment or any of the
other Loan Documents or to the transactions contemplated hereby.

         6.11 ENTIRE AGREEMENT. THIS THIRD AMENDMENT AND ALL OTHER INSTRUMENTS,
DOCUMENTS AND AGREEMENTS EXECUTED AND DELIVERED IN CONNECTION WITH THIS THIRD
AMENDMENT EMBODY THE FINAL, ENTIRE AGREEMENT AMONG THE PARTIES HERETO AND
SUPERSEDE ANY AND ALL PRIOR COMMITMENTS, AGREEMENTS, REPRESENTATIONS AND
UNDERSTANDINGS, WHETHER WRITTEN OR ORAL, RELATING TO THIS AMENDMENT, AND MAY
NOT BE CONTRADICTED OR VARIED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR
SUBSEQUENT ORAL AGREEMENTS OR DISCUSSIONS OF THE PARTIES HERETO. THERE ARE NO
ORAL AGREEMENTS AMONG THE PARTIES HERETO.

         Executed as of the date first written above.


                                BORROWER:

                                INDUSTRIAL HOLDINGS, INC., a Texas corporation

                                By:
                                   -------------------------------
                                Michael N. Marsh
                                President & Chief Executive Officer


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                                ADDRESS FOR NOTICES:

                                Industrial Holdings, Inc.
                                7135 Ardmore
                                Houston, Texas 77054
                                Fax No.: 713-749-9642
                                Telephone No.: 713-747-1025
                                Attention: Mr. Stephen W. Nash


                                AGENT:


                                COMERICA BANK-TEXAS

                                By:
                                   ---------------------------------
                                Robin M. Kain
                                Vice President

                                ADDRESS FOR NOTICES:

                                Comerica Bank - Texas
                                P.O. Box 650282
                                Dallas, Texas 75265-0282
                                Fax No.: (214) 969-6416
                                Telephone No.: (214) 969-6472
                                Attention: Mr. Gary Orr
                                            MC 6507

                                WITH A COPY TO:
                                Comerica Bank - Texas
                                P.O. Box 650282
                                Dallas, Texas  75265-0282
                                Fax No.: (214) 589-4724
                                Telephone No.: (214) 589-4708
                                Attention: Robin M. Kain
                                            MC 6510











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                                BANKS:

Commitment:                     COMERICA BANK-TEXAS
$27,272,727.28
                                By:
                                   --------------------------------
                                           Robin M. Kain
                                           Vice President


                                ADDRESS FOR NOTICES:

                                Comerica Bank - Texas
                                P.O. Box 650282
                                Dallas, Texas 75265-0282
                                Fax No.: (214) 969-6416
                                Telephone No.: (214) 969-6472
                                Attention: Mr. Gary Orr
                                               MC 6507
                                WITH A COPY TO:

                                Comerica Bank - Texas
                                P.O. Box 650282
                                Dallas, Texas  75265-0282
                                Fax No.: (214) 589-4724
                                Telephone No.: (214) 589-4708
                                Attention: Robin M. Kain
                                               MC 6510

                                 LENDING OFFICE FOR BASE RATE ADVANCES

                                 Comerica Bank
                                 1508 West Mockingbird
                                 Dallas, Texas 75235

Commitment:                      HIBERNIA NATIONAL BANK
$9,090,909.09

                                 By:
                                    -------------------------------
                                          Tammy Angelety
                                          Vice President

                                 ADDRESS FOR NOTICES:

                                 Hibernia National Bank
                                 225 Barone Street., 10th Fl.
                                 New Orleans, Louisiana 70112
                                 Fax No.: (504) 533-5099
                                 Telephone No.: (504) 533-2045
                                 Attention: Ms. Tammy Angelety




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      Guarantors hereby consent and agree to this Third Amendment and agree that
the Guaranty shall remain in full force and effect and shall continue to be the
legal, valid and binding obligation of Guarantors enforceable against Guarantors
in accordance with its terms.

GUARANTORS:

A & B Bolt and Supply, Inc., a Louisiana corporation
The Rex Group, Inc., a Texas corporation
Rex Machinery Sales, Inc., a Texas corporation d/b/a
      Rex/Paul's Machine/Sales
Rex Machinery Movers, Inc., a Texas corporation
      d/b/a Ideal Products
USC Holdings, Inc., a Texas corporation
      (f/k/a U.S. Crating, Inc.)
First Texas Credit Corporation, a Texas corporation
Landreth Engineering Company, a Texas corporation
Pipeline Valve Specialty, Inc., a Texas corporation
      (f/k/a Industrial Municipal Supply Company)
Bolt Manufacturing Co., Inc., a Texas corporation,
      d/b/a Walker Bolt Manufacturing Co., Inc.
LSS-Lone Star-Houston, Inc., a Texas corporation
American Rivet Company, Inc., an Illinois
      corporation
Manifold Valve Services, Inc., a Delaware
      corporation, d/b/a Rogers Equipment & Supply
      Company
Philform, Inc., a Michigan corporation
GHX, Incorporated, a Texas corporation
Regal Machine Tool, Inc., a Texas corporation, f/k/a
      Rex Machine Tool, Inc.
WHIR Acquisition, Inc., a Texas corporation,
      d/b/a Ameritech Fastener Manufacturing
Moores Pump and Supply, Inc., a Louisiana
      corporation
GHX, Incorporated of Louisiana, a Louisiana
      corporation
Beaird Industries, Inc., a Delaware corporation
United Wellhead Services, Inc., a Texas corporation


By:
   ------------------------------------
Name:   Michael N. Marsh
Title:  Chief Executive Officer








                                      EX-27
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                                   EXHIBIT "A"

                           Existing Events of Default



         The Borrower warrants that if is presently in default of only the
following provisions of the Agreement:


1.       Failure to pay when due $15,000,000.00 owing to EnSerCo.

2.       Failure to comply with Section __ (requiring ____________________) and
         Section __ (requiring _______________________) of the Borrower's
         agreement with Heller Financial, Inc.




























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