<PAGE>   1
                                                            EXHIBIT 10(n)

                           [COMERICA BANK LETTERHEAD]




March 22, 1996


Detrex Corporation
24901 Northwestern Highway, Suite 500 
Southfield, Michigan 48075

The Elco Corporation
1000 Belt Line Street
Cleveland, Ohio 44109

Harvel Plastics, Inc.
P.O. Box 757
Easton, Pennsylvania 18042

Seibert-Oxidermo, Inc.
16255 Wahrman
Romulus, Michigan 48174

Attn:  Mr. Gerald J. Israel

RE:    FINANCING ARRANGEMENTS AMONG COMERICA BANK AND NBD BANK (COLLECTIVELY,
       THE "BANKS"), COMERICA BANK AS AGENT FOR THE BANKS ("AGENT"), AND
       DETREX CORPORATION, THE ELCO CORPORATION, HARVEL PLASTICS, INC. AND
       SEIBERT-OXIDERMO INC. (COLLECTIVELY, "COMPANIES")


Dear Mr. Israel:

Please refer to the Credit Agreement dated as of March 11, 1994, the First
Amendment to Credit Agreement and Waiver dated as of December 31, 1994 both
among Agent, the Banks and the Companies (collectively, the "Credit Agreement")
and any and all documents, instruments and agreements executed in connection
with the financing arrangements from Agent and the Banks or any of them to the
Companies (collectively with the Credit Agreement, the "Loan Documents"). All
amounts due from the Companies to Agent and the Banks, whether now or in the
future, contingent, fixed, primary and/or secondary, including, but not limited
to, principal, interest, inside and outside counsel fees, audit fees, costs,
expenses and any and all other charges provided for in the Loan Documents shall
be known, in the aggregate, as the "Liabilities." All capitalized terms not
defined in this agreement ("Agreement") shall have the meanings described in
the Loan Documents.


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                           [COMERICA BANK LETTERHEAD]


Mr. Gerald J. Israel
March 22, 1996
Page 2

As of March 7, 1996 the Liabilities were as follows:

Loans (note amount and date)                             Principal
----------------------------                            ----------
Comerica Revolving Credit Loan                          $5,666,695 
NBD Revolving Credit Loan                                2,833,305
Letter of Credit Reimbursement                             611,221 
   Obligations

The amounts set forth above are exclusive of interest and costs and expenses
(including, but not limited to, inside and outside counsel fees), which amounts
shall be immediately due and payable from the Companies to Agent and/or the
Banks when accrued or incurred.

Without limitation, the Companies are in default of Section 12.1(a) of the
Credit Agreement on account of its failure to bring Formula Debt into compliance
with Lending Availability (as defined in Section 1.60 of the Credit Agreement).
This out-of-formula condition was: $2,597,364 as reported on Agent's collateral
audit report dated November 20, 1995, $1,296,000 as reported on the Companies'
Borrowing Base Report dated November 30, 1995, $2,306,421 on the Companies'
Borrowing Base Report dated December 31, 1995, $4,160,095 based on the
Companies' Borrowing Base Report dated January 26, 1996, $1,714,076 based on the
Companies' Borrowing Base Report dated January 31, 1996, $1,643,051 based on the
Companies' Borrowing Base Report dated February 10, 1996, $2,574,531 based on
the Companies' Borrowing Base Report dated February 17, 1996 and $2,717,466
based on the Companies' Borrowing Base Report dated February 24, 1996.

The Companies represent to Agent and the Banks that they know of no other
defaults under the Loan Documents, except that the Companies anticipate that
their financial statements for the period ended December 31, 1995 will show a
violation of Sections 11.1, 11.2 and 11.4 of the Credit Agreement (the
"Financial Covenant Defaults").

As a result of the Events of Default identified above, the Agent and the Banks
have the right to accelerate the Liabilities and demand payment in full of the
Liabilities.

The Companies have requested that Agent and the Banks forbear from accelerating
and demanding payment of the Liabilities in order to permit the Companies until
April 15, 1996 to arrange for new financing by a lending institution to pay in
full the Liabilities.

In response to the Companies' request and provided as to the Financial Covenant
Defaults that the audited financial statements for the fiscal year ended
December 31, 1995 indicate a Net Loss after taxes of $1,969,303 or less, a
Tangible Net Worth of $15,834,200 or more and a Leverage Ratio of 2.6 to 1 or
less, and


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                           [COMERICA BANK LETTERHEAD]


Mr. Gerald J. Israel
March 22, 1996
Page 3

subject to the Companies' written acceptance of the following conditions, Agent
and the Banks are willing to forbear until April 15, 1996 (as such date may be
extended under paragraph 12 below), from accelerating and demanding payment of
the Liabilities:

1.   The Companies acknowledge the Liabilities as set out in the Loan
     Documents, the amount of the Liabilities and the existence of the
     defaults.  The Companies acknowledge that a demand for payment by the
     Agent and the Banks would be timely, proper and within their rights under
     the Loan Documents and that there is no setoff, defense or counterclaim,
     in law or in equity, of any kind or nature, to the Liabilities.

2.   Future administration of the Liabilities and the financing arrangements
     among Agent, the Banks and the Companies shall continue to be governed by
     the covenants, terms and conditions of the Loan Documents, executed prior
     to the date of this Agreement, which are incorporated in this Agreement,
     except to the extent that the Loan Documents are superseded, amended,
     modified or supplemented by this Agreement or are inconsistent with this
     Agreement, then this Agreement shall govern.  The Companies reaffirm,
     ratify and confirm the Loan Documents and the liens, assignments and
     security interests granted to Agent and the Banks under the Loan Documents
     which shall continue to secure the Liabilities.

3.   The Companies acknowledge and agree that the several commitments of the
     Banks set forth in Section 2.1 of the Credit Agreement are terminated and
     that the Banks are under no obligation to advance funds or extend credit
     to the Companies under the Loan Documents, or otherwise.

4,   Additional advances under the Credit Agreement are subject to maintaining
     Formula Debt within the Lending Availability and are to be at the
     discretion of Agent and the Banks and in such manner and amount as Agent
     and the Banks deem appropriate.

5.   In addition to the reporting requirements set forth in the Loan
     Documents, effective February 1, 1996, the Companies shall provide to
     Agent the following: (i) detailed monthly account payable reports to be
     received by Agent within 20 days of month end; (ii) detailed monthly
     accounts receivable agings and the Agent's standard month-end reports all
     certified by a Responsible Officer to be received by Agent within 20 days
     of month end; (iii) weekly reports of accounts receivable on Agent's
     standard forms certified by a Responsible Officer



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                           [COMERICA BANK LETTERHEAD]

Mr. Gerald J. Israel
March 22, 1996
Page  4

     to be received by Agent the following Thursday of each week; (iv) monthly
     inventory report of raw material and finished goods on Agent's standard
     form to be received by Agent within 20 days of month end for The Elco
     Corporation, Harvel Plastics, Inc., and Seibert-Oxidermo, Inc.; (v)
     monthly internal results by business unit to be received by Agent within
     30 days of month end; (vii) quarterly balance sheets for The Elco
     Corporation, Harvel Plastics, Inc. and Seibert-Oxidermo, Inc. to be
     received by Agent within 30 days of quarter end; (viii) annual financial
     statements for Harvel Plastics, Inc. within 90 days of year end prepared
     by Detrex Corporation's auditor; and (ix) a report of current accounts
     receivable and customer lists with current addresses to be received by
     Agent within 5 days of the date of this Agreement and weekly thereafter.

6.   The Companies agree:

          (i)  Equipment and Fixtures. Each of the Companies agree to grant a
               first, perfected security interest in its equipment and fixtures
               to Agent to secure the Liabilities.  Concurrently with their
               execution of this Agreement, each of the Companies shall deliver
               a Security Agreement (Equipment) in the form attached as Exhibit
               A and will do all acts and things and will execute all writings
               (including financing statements) requested by Agent to establish,
               maintain and continue a first, perfected security interest in
               the equipment and fixtures.

          (ii) Stock in Subsidiaries. Detrex Corporation agrees to grant a
               first, perfected security interest in 100% of the outstanding
               capital stock of each of its Subsidiaries, including The Elco
               Corporation, Detrex Industrial Water Treatment, Inc., Wayne
               Chemical Products Company and Seibert-Oxidermo, Inc. The Elco
               Corporation agrees to grant a first, perfected security interest
               in 100% of the outstanding capital stock of its Subsidiary,
               ELDISC Export Co., and all of its capital stock (representing 85%
               of the outstanding capital stock) of its Subsidiary, Harvel
               Plastics, Inc. Concurrently with their execution of this
               Agreement, Detrex Corporation and The Elco




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                           [COMERICA BANK LETTERHEAD]


Mr. Gerald J. Israel
March 22, 1996
Page 5

               Corporation shall each deliver a Security Agreement in the form
               attached as Exhibit B and will do all acts and things and will
               execute all writings (including delivery of the certificates
               evidencing the capital stock and assignments separate from
               certificate) requested by Agent to establish, maintain and
               continue a first, perfected security interest in the stock of
               such Subsidiaries.

         (iii) Real Estate. The Companies agree to grant a first priority
               mortgage on four real estate parcels commonly known as 325 Emmett
               Avenue, Bowling Green, Kentucky 42101, 401 Emmett Avenue, Bowling
               Green, Kentucky 42101, 26000 Capitol Avenue, Redford, Michigan
               48239 and 300 Kuebler Rd., Easton, Pennsylvania.  Concurrently
               with their execution of this Agreement, the Companies will cause
               the owners of such real estate parcels to deliver a Mortgage to
               Agent in the form attached as Exhibit C and will do all acts and
               things and will execute all writings requested by Agent to
               establish, maintain and continue a first, perfected mortgage lien
               in such real estate.

          (iv) Acknowledgement regarding Tax Refunds.  The Companies acknowledge
               that they previously granted a first perfected security interest
               in their general intangibles, including tax refunds, to Agent for
               the benefit of the Banks,

          (v)  Consent of Minority Shareholders of Harvel Plastics, Inc. By
               April 1, 1996, the Elco Corporation shall obtain the consent of
               the minority shareholders of Harvel Plastics, Inc. to this
               Agreement, including the pledge of the stock of Harvel Plastics,
               Inc., and shall waive or amend the by-laws of Harvel Plastics,
               Inc to permit the pledge of such stock to Agent, and Agent's
               subsequent exercise of its power of sale as secured party. The
               minority shareholders of Harvel Plastics, Inc. may retain their
               right of first refusal with regard to the sale of the pledged
               stock.


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                           [COMERICA BANK LETTERHEAD]

Mr. Gerald J. Israel
March 22, 1996
Page 6


          (vi) NBD Equipment Finance, Inc./Comerica Leasing Corporation.  The
               Companies agree that all of the security (whether personal
               property or real estate) granted to Agent to secure the
               Liabilities shall also secure all amounts due from the Companies
               to either of NBD Equipment Finance, Inc. and Comerica Leasing
               Corporation, whether now or in the future, contingent,
               fixed, primary and/or secondary, including but not limited to,
               principal, interest, inside and outside counsel fees, costs,
               expenses and any and all other charges, subject only to the
               execution by NBD Equipment Finance, Inc. and Comerica Leasing
               Corporation of an intercreditor agreement in form and substance
               satisfactory to Agent and the Banks (the requirement of an
               intercreditor agreement is for the benefit of the Banks and may
               be waived by them).

7.   The definition of "Lending Availability" in the Credit Agreement is amended
     to mean as of any date of determination thereof, the sum of (a) eighty
     percent (80%) of Eligible Accounts, and (b) Four Million Four Hundred Fifty
     Thousand Dollars ($4,450,000); provided, however, effective upon receipt by
     the Companies of each of their federal tax refund on account of the tax
     year ended December 31, 1995 (estimated by Companies at $1,887,741), their
     federal tax refund or account of the tax year ended December 31, 1992
     (estimated by Companies at $1,261,949 plus interest) and the proceeds of
     the sale of any real estate, the $4,450,000 overformula amount shall reduce
     permanently by an amount equal to such receipt. Notwithstanding the
     provisions of paragraphs 6 (iv) and 11, provided that there is no default
     under this Agreement or the Loan Documents, the Companies shall apply to
     the Revolving Credit Loan not less than $1,000,000 of the 1995 tax refund
     and may retain and use up to $887,741 of the 1995 tax refund for ordinary
     working capital purposes.

8.   All future Advances, if any, under the Credit Agreement and the Loan
     Documents, including the continuation of any outstanding Eurodollar-based
     Advance, shall be Prime-based Advances and not the Eurodollar-based
     Advances. Effective as of January 1, 1996, all Advances shall bear interest
     at the default rates specified in Section 5.1 of the Credit Agreement until
     execution of this Agreement by the Companies by the deadline set forth in
     paragraph 22




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                           [COMERICA BANK LETTERHEAD]


Mr. Gerald J. Israel
March 22, 1996
Page   7

      below.  Effective as of the date of the execution and delivery by
      Companies of this Agreement and the other documents required to be
      delivered concurrently therewith all by the deadline set forth in
      paragraph 22 below: (a) the Agent and Banks shall withdraw the imposition
      of the default rate; (b) the definition of if Prime-based Rate" in the
      Credit Agreement shall be amended to mean that per annum rate of
      interest which is one percent (1%) plus the Prime Rate; and (c) the
      definition of "Applicable Eurodollar Margin" in the Credit Agreement,
      which shall be effective for all outstanding Eurodollar-based Advances,
      shall be amended to mean three and one quarter percent (3-1/4%).

9.    Certain covenants set forth in the Credit Agreement are amended as
      follows:

               (i)  Section 11.8(c).  Section 11.8(c) is amended to change
                    "Five Hundred Thousand Dollars ($500,000)" to "One Hundred
                    Thousand Dollars ($100,000).

              (ii)  Section 11.8(d), Section 11.8(d) is deleted.

             (iii)  Section 12.1(f). Clause (i) of Section 12.1(f) is amended
                    to change "Two Hundred Fifty Thousand Dollars ($250,000)" to
                    "Fifty Thousand Dollars ($50,000)."

              (iv)  Section 12.1(i), Section 12.1(i) is amended to change "Five
                    Hundred Thousand Dollars ($500,000)" to "One Hundred
                    Thousand Dollars ($100,000)."

10.   The Companies acknowledge and agree the Loan Documents require them to
      reimburse Agent and Banks for any and all costs and expenses of Agent and
      Banks, including, but not limited to, all inside and outside counsel fees
      of Agent and Banks whether in relation to drafting, negotiating or
      enforcement or defense of the Loan Documents or this Agreement, including
      any preference or disgorgement actions as defined in this Agreement, any
      fee for cancellation of pending appraisals of the Companies' real estate,
      any fees for real estate title searches (but not mortgage title insurance
      policies) and all of the audit



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                           [COMERICA BANK LETTERHEAD]



Mr, Gerald J. Israel
March 22, 1996
Page  8

     fees of Agent or the Banks, incurred by them in connection with the
     Liabilities, administration of the Liabilities and/or any efforts of Agent
     and Banks to collect or satisfy all or any part of the Liabilities. The
     Companies shall immediately reimburse Agent and Banks for all of their
     costs and expenses upon demand.  The Companies shall also defend and hold
     harmless the Banks and the Agent from any claim or damages of the
     Companies, or any of them, or any third party against Bank arising from or
     relating to the Liabilities, the Loan Documents, this Agreement or the
     business relationship among the Banks, the Agent and the Companies.

11.  The Companies, except for Harvel Plastics, Inc., acknowledge and agree
     that they shall hereafter be on a remittance basis (as described in the
     security agreements) except the Companies shall not be required to have
     account debtors send payments directly to the lock box at Agent unless the
     Companies have failed to deliver to Agent and the Banks by April 15, 1996
     a written, commitment from a lending institution to make a loan that will
     pay in full the Liabilities; each of the Companies, except for Harvel
     Plastics, Inc., shall immediately surrender all of their cash inflows to
     Commercial Lending Services, Comerica Bank, P.O. Box 75000, Detroit,
     Michigan 48275-3212, or such other person and/or entity as Bank may
     designate, in the form of and as and when received by them.  If the
     Companies have failed to deliver to Agent and the Banks by April 1, 1996 a
     written, commitment from a lending institution to make a loan that will
     pay in full the Liabilities, then, in order to insure the integrity of the
     remittance basis procedure, each Company, except for Harvel Plastics,
     Inc., must maintain all of its bank accounts at Comerica (except for
     payroll and petty cash accounts).

12.  Agent and the Banks agree that if on or before April 15, 1996 the
     Companies deliver to them a written, commitment from a lending institution
     to make a loan that will pay in full the Liabilities and such commitment
     is satisfactory in form and substance to Agent and the Banks in their sole
     discretion and if no default under this Agreement or further default under
     the Loan Documents has occurred, then in that event Agent and the Banks
     will extend the forbearance period for up to sixty days (but not to a date
     beyond the expiration date of the commitment) at the request of the
     Companies.  If the forbearance period is so extended, any default by the
     Companies under the commitment or its expiration or cancellation would be
     a default under this Agreement.



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                           [COMERICA BANK LETTERHEAD]


Mr. Gerald J. Israel
March 22, 1996
Page  9

13.  The Companies authorize Agent to charge interest, costs and expenses and
     other payments required of the Companies under this Agreement or the Loan
     Documents directly to their checking accounts maintained at Agent.

14.  To the extent any payment received by Agent or the Banks is deemed a
     preference, fraudulent transfer or otherwise by a court of competent
     jurisdiction which requires the transferee to disgorge such payment, then
     the Liabilities shall be reinstated to the extent of any such
     disgorgement.

15.  The Companies agree to execute any and all additional or supplemental
     documentation, and provide such further assistance and assurances as Agent
     or the Banks may require, in the sole and absolute discretion of Agent and
     the Banks, to give full effect of the terms, conditions and intentions of
     this Agreement.

16.  This Agreement shall be governed and controlled in all respects by the
     laws of the State of Michigan, including interpretation, enforceability,
     validity and construction,

17.  Agent and the Banks expressly reserve the right to exercise any or all
     rights and remedies provided under the Loan Documents and applicable law
     except as modified by this letter agreement. Any failure to immediately
     exercise such rights and remedies shall not be construed as a waiver or
     modification of those rights or an offer of forbearance.

18.  Each of the Companies represents and warrants to the Agent and the Banks
     that they have received direct and substantial economic benefit from all of
     the Liabilities and that they will continue to receive direct and
     substantial economic benefit from such loans, and from any other loans made
     or which may be made in the future to the Companies.

19.  This Agreement will inure to the benefit of the Agent and each of the
     Banks and all of their respective past, present and future parents,
     subsidiaries, affiliates, predecessors and successor corporations and all
     of their subsidiaries and affiliates.

20.  EACH OF THE COMPANIES, THE BANKS AND THE AGENT ACKNOWLEDGE AND AGREE THAT
     THE RIGHT TO TRIAL BY JURY IS A CONSTITUTIONAL ONE, BUT THAT IT MAY BE
     WAIVED.  EACH PARTY, AFTER CONSULTING (OR HAVING HAD THE OPPORTUNITY TO


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                           [COMERICA BANK LETTERHEAD]


Mr. Gerald J. Israel
March 22, 1996
Page  10

     CONSULT) WITH COUNSEL OF THEIR CHOICE, KNOWINGLY AND VOLUNTARILY, AND FOR
     THEIR MUTUAL BENEFIT WAIVES ANY RIGHT TO TRIAL BY JURY IN THE EVENT OF
     LITIGATION REGARDING THE PERFORMANCE OR ENFORCEMENT OF, OR IN ANY WAY
     RELATED TO, THE LOAN DOCUMENTS, THIS AGREEMENT OR THE LIABILITIES.

21.  EACH OF THE COMPANIES, IN EVERY CAPACITY, INCLUDING, BUT NOT LIMITED TO,
     AS SHAREHOLDERS, PARTNERS, OFFICERS, DIRECTORS, INVESTORS AND/OR
     CREDITORS OF THE COMPANIES, OR ANY ONE OR MORE OF THEM, HEREBY WAIVE,
     DISCHARGE AND FOREVER RELEASE AGENT, THE BANKS AND THEIR EMPLOYEES,
     OFFICERS, DIRECTORS, ATTORNEYS, STOCKHOLDERS AND SUCCESSORS AND ASSIGNS,
     FROM AND OF ANY AND ALL CLAIMS, CAUSES OF ACTION, DEFENSES, COUNTERCLAIMS
     OR OFFSETS AND/OR ALLEGATIONS THE COMPANIES OR ANY OF THEM MAY HAVE OR MAY
     HAVE MADE AT ANY TIME UP THROUGH AND INCLUDING THE DATE OF THIS AGREEMENT,
     AGAINST ANY OR ALL OF AGENT, THE BANKS AND THEIR EMPLOYEES, OFFICERS,
     DIRECTORS, ATTORNEYS, STOCKHOLDERS AND SUCCESSORS AND ASSIGNS.

22.  The Companies shall properly execute and deliver this Agreement to the
     undersigned by no later than 5:00 p.m. on March 22, 1996.

Agent and the Banks reserve the right to terminate the forbearance provided for
in this Agreement prior to April 15, 1996 (or any extended date as provided
under paragraph 12 above), in the event of any new defaults or aggravation of
existing defaults under the Loan Documents, defaults under this Agreement, in
the event of further deterioration in the financial condition of the Companies,
or any of them, or deterioration in the Collateral, and/or in the sole and
absolute discretion of Agent and the Banks at any time and for any reason.


COMERICA BANK, Agent



By: Mark A. Reifel 
    -------------------------
    Mark A. Reifel
Its:  Assistant Vice President

cc:   NBD Bank


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                           [COMERICA BANK LETTERHEAD]


Mr. Gerald J. Israel
March 22, 1996
Page 11

ACKNOWLEDGED AND AGREED:

DETREX CORPORATION

By:  G.J. ISRAEL                     Date: March 22             , 1996
   --------------------------             ----------------------

Its: V.P. - FINANCE
    -------------------------


THE ELCO CORPORATION

By:  G.J. ISRAEL                     Date: March 22             , 1996
   --------------------------             ----------------------

Its: TREASURER
    -------------------------

HARVEL PLASTICS, INC,

By:  G.J. ISRAEL                     Date: March 22             , 1996
   --------------------------             ----------------------

Its:  DIRECTOR
    -------------------------

SEIBERT-OXIDERMO, INC,

By:  G.J. ISRAEL                     Date: March 22             , 1996
   --------------------------             ----------------------

Its:  TREASURER
    -------------------------