SECOND AMENDMENT AGREEMENT

                  THIS SECOND AMENDMENT AGREEMENT (this "Amendment"), is entered
into as of January 31, 1997, between Komag, Incorporated, a Delaware corporation
(the  "Borrower"),  and The  Industrial  Bank of Japan,  Limited,  San Francisco
Agency (the "Bank").

                  WHEREAS,  the  Borrower  and the Bank are  parties to a Credit
Agreement  dated as of December  15, 1995 (as amended  prior to the date hereof,
the "Credit Agreement");

                  WHEREAS,  the  Borrower has  requested  that the Bank agree to
increase the Commitment to $50,000,000  and to make certain other  amendments to
the Credit  Agreement  and the Bank has agreed to such  request,  subject to the
terms and conditions hereof;

                  NOW,  THEREFORE,  in consideration  of the mutual  agreements,
provisions and covenants contained herein, the parties hereto agree as follows:

                  1.  Definitions.  All capitalized terms used in this Amendment
(including in the recitals  hereof) and not otherwise  defined herein shall have
the meanings assigned to them in the Credit Agreement.

                  2. Amendment to the Credit Agreement.

                           (a) Section  1.01 of the Credit  Agreement  is hereby
amended by deleting the definition of "Commitment" in its entirety and replacing
it with the following

                           "Commitment":   The   Commitment   of  Bank  to  make
         Revolving  Loans to  Borrower  pursuant  to  Article  II up to, but not
         exceeding, at any time outstanding the amount of $50,000,000.

                           (b) Section  1.01 of the Credit  Agreement  is hereby
amended by adding the following definitions thereto:

                           "Existing  Loan": The Revolving Loan in the principal
         amount of $35,000,0009  outstanding on the date of the Second Amendment
         Agreement.

                           "Interim  Loan":  Any Revolving  Loan  initially made
         after the date of the Second  Amendment  Agreement and before  December
         29, 1997,  and any  conversion  or  continuation  thereof made prior to
         December 29, 1997.

                           "Second  Amendment  Agreement":  The Second Amendment
         Agreement, dated as of January 31, 1997, between Borrower and Bank.

                                       1.
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                           (c) Section 2.1(e) of the Credit  Agreement is hereby
amended by inserting at the end of the paragraph the following sentence:

         Pursuant  to Section  8.6(a)  hereof,  Bank may from time to time grant
         participations  (each a  "Participation")  in the  Revolving  Loans and
         Commitment  to one or  more  participants  (each a  "Participant");  if
         Borrower  should  at any time or from  time to time  purchase  any such
         Participation  from  a  Participant,  then  Borrower  shall  give  Bank
         immediate  notice of such  purchase and the  outstanding  amount of the
         Revolving  Loans shall be reduced to the extent of the interest in such
         Revolving  Loans so  purchased  by  Borrower  (i.e.,  the  purchase  by
         Borrower of the interest of such  Participant  in the  Revolving  Loans
         shall be treated as a prepayment by Borrower of the Revolving  Loans to
         the extent of such interest so purchased),  and the Commitment shall be
         reduced by such  selling  Participant's  Participation  interest in the
         Commitment  allocated to such  Participant  under the  Participation so
         purchased by Borrower.

                           (d)  Section  2.1 of the Credit  Agreement  is hereby
amended to add a Section 2.1(i)  thereto to be inserted  after existing  Section
2.1(h) as follows:

                  (i) Second Amendment  Transition.  Any other provision in this
         Agreement to the contrary  notwithstanding:  (i) unless the maturity of
         the Existing Loan is accelerated  pursuant to the provisions of Section
         7.1 hereof,  the Existing Loan may not be repaid except on December 29,
         1997,  (ii) no Interim Loan which is a Eurodollar Rate Loan may have an
         Interest  Period ending after  December 29, 1997,  unless such Interest
         Period  commences  on December 29,  1997,  and (iii) from  November 29,
         1997, to December 29, 1997,  Interim Loans may be made,  converted,  or
         continued only as Prime Rate Loans.

                           (e) Section 8.6(D) of the Credit  Agreement is hereby
amended by inserting  the phrase "or amend or waive the  provisions  of Sections
6.2(a), (b) or (c)" after the word "sentence".

                           (f) The form of  Exhibit  B to the  Credit  Agreement
shall be deleted and the form of Exhibit B attached  hereto shall be inserted in
lieu thereof.

                  3. Conditions of Effectiveness. The effectiveness of Section 2
of this Amendment  shall be subject to the  conditions  that the Bank shall have
received,  on or before the date hereof,  (a) a copy of this Amendment  executed
and delivered by a duly authorized officer of the Borrower, (b) a certificate of
the  Secretary or Assistant  Secretary of the  Borrower,  dated the date hereof,
certifying a copy of  resolutions  of the  Borrower's  Board of  Directors  that
approve the execution and delivery of this  Amendment,  (c) a promissory note in
the  form  attached  as  Exhibit  B  hereto  executed  and  delivered  by a duly
authorized officer of the Borrower,  and (d) a participation  agreement executed
and delivered by The First National Bank of Chicago.

                                       2.
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                  4.     Miscellaneous.

                           (a) Credit Agreement  Otherwise Not Affected.  Except
as  expressly  amended  pursuant  hereto,  the  Credit  Agreement  shall  remain
unchanged  and in full force and effect and is hereby  ratified and confirmed in
all respects.

                           (b)  Counterparts.  This Amendment may be executed by
one or  more  of the  parties  to  this  Amendment  in any  number  of  separate
counterparts,  each of which, when so executed, shall be deemed an original, and
all of said  counterparts  taken  together shall be deemed to constitute but one
and the same instrument. A set of the copies of this Amendment signed by all the
parties shall be lodged with the Borrower and the Bank.

                           (c) Governing Law. THIS  AMENDMENT  SHALL BE GOVERNED
BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF CALIFORNIA.

                                       3.
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                  IN WITNESS  WHEREOF,  the  parties  hereto  have  caused  this
Amendment to be duly executed and delivered by their proper and duly  authorized
officers as of the day and year first above written.

                                    KOMAG, INCORPORATED

                                    By:     /s/ William L. Potts, Jr.
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                                    Title: SVP, CFO
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                                    THE INDUSTRIAL BANK OF JAPAN,
                                    LIMITED, acting through its San 
                                    Francisco Agency

                                    By:
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                                    Title: 
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