<PAGE>
 
                                                                     EXHIBIT 3.2
 
                          CERTIFICATE OF INCORPORATION
                                       OF
                              STX CHEMICALS CORP.

     The undersigned natural person, acting as an incorporator of a corporation
under the General Corporation Law of the State of Delaware, hereby adopts the
following Certificate of Incorporation for such corporation:

                                   ARTICLE I

                                      NAME
                                      ----

     The name of the corporation is "STX Chemicals Corp." (the "Corporation").


                                   ARTICLE II

                          REGISTERED OFFICE AND AGENT
                          ---------------------------

     The street address of the initial registered office of the Corporation is
1209 Orange Street, Wilmington, New Castle County, Delaware 19801, and the name
of its initial registered agent at such address is The Corporation Trust
Company.

                                  ARTICLE III

                                    PURPOSE
                                    -------

     The purpose for which the Corporation is organized is to engage in any
lawful act or activity for which corporations may be organized under the General
Corporation Law of Delaware.

                                   ARTICLE IV

                                     SHARES
                                     ------

     The aggregate number of shares which the Corporation has authority to issue
is 1,000 shares, par value $0.01 per share.  The shares are designated as common
stock and have identical rights and privileges in every respect.
<PAGE>
 
                                   ARTICLE V

                                  INCORPORATOR
                                  ------------

     The name and address of the incorporator is:

                    Thomas M. Hart III
                    c/o Andrews & Kurth L.L.P.
                    4200 Texas Commerce Tower
                    600 Travis
                    Houston, Texas 77002

                                   ARTICLE VI

                               INITIAL DIRECTORS
                               -----------------

     The number of directors constituting the initial Board of Directors is one
and the name and address of the person who is to serve as director until his
successor is duly elected and qualified is:

                    Frank J. Hevrdejs
                    Eight Greenway Plaza, Suite 702
                    Houston, Texas 77046

                                  ARTICLE VII

                 LIMITATION OF PERSONAL LIABILITY OF DIRECTORS
                 ---------------------------------------------

     No director (including any advisory director) of the Corporation shall be
liable to the Corporation or its stockholders for monetary damages for breach of
fiduciary duty as a director, except for liability (i) for any breach of the
director's duty of loyalty to the Corporation or its stockholders, (ii) for acts
or omissions not in good faith or which involve intentional misconduct or a
knowing violation of law, (iii) under Section 174 of the General Corporation Law
of the State of Delaware or (iv) for any transaction from which the director
derived an improper personal benefit.

                                  ARTICLE VIII

                                   INDEMNITY
                                   ---------

     Section 1.  The Corporation shall indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, 

                                      -2-
<PAGE>
 
whether civil, criminal, administrative, or investigative (other than an action
by or in the right of the Corporation) by reason of the fact that he is or was a
director, officer, employee, or agent of the Corporation or is or was serving at
the request of the Corporation as a director, officer, employee, or agent of
another corporation, partnership, joint venture, trust, or other enterprise,
against expenses (including attorneys' fees), judgments, fines, and amounts paid
in settlement actually and reasonably incurred by him in connection with such
action, suit or proceeding if he acted in good faith and in a manner he
reasonably believed to be in or not opposed to the best interests of the
Corporation, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful. The termination of any
action, suit or proceeding by judgment, order, settlement, conviction, or upon a
plea of nolo contendere or its equivalent, shall not, of itself, create a
presumption that the person did not act in good faith and in a manner which he
reasonably believed to be in or not opposed to the best interests of the
Corporation, and, with respect to any criminal action or proceeding, had
reasonable cause to believe that his conduct was unlawful.

     Section 2.  The Corporation shall indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action or suit by or in the right of the Corporation to procure a
judgment in its favor by reason of the fact that he is or was a director,
officer, employee, or agent of the Corporation, or is or was serving at the
request of the Corporation as a director, officer, employee, or agent of another
corporation, partnership, joint venture, trust, or other enterprise against
expenses (including attorneys' fees) actually and reasonably incurred by him in
connection with the defense or settlement of such action or suit if he acted in
good faith and in a manner he reasonably believed to be in or not opposed to the
best interests of the Corporation and except that no indemnification shall be
made in respect of any claim, issue or matter as to which such person shall have
been adjudged to be liable to the Corporation unless and only to the extent that
the Delaware Court of Chancery or the court in which such action or suit was
brought shall determine upon application that, despite the adjudication of
liability but in view of all the circumstances of the case, such person is
fairly and reasonably entitled to indemnity for such expenses which the Delaware
Court of Chancery or such other court shall deem proper.

     Section 3.  To the extent that a director, officer, employee, or agent of
the Corporation has been successful on the merits or otherwise in defense of any
action, suit or proceeding referred to in Sections 1 and 2, or in defense of any
claim, issue or matter therein, he shall be indemnified against expenses
(including attorneys' fees) actually and reasonably incurred by him in
connection therewith.

     Section 4.  Any indemnification under Sections 1 and 2 (unless ordered by a
court) shall be made by the Corporation only as authorized in the specific case
upon a determination that indemnification of the director, officer, employee, or
agent is proper in the circumstances because he has met the applicable standard
of conduct set forth in Sections 1 and 2.  Such determination shall be made (i)
by the Board of Directors by a majority vote of a quorum consisting of directors
who were not parties to such action, suit or proceeding, (ii) if such a quorum
is not obtainable, or, even if obtainable, if a quorum of disinterested
directors so directs, by independent legal counsel in a written opinion, or
(iii) by the stockholders.  Notwithstanding the foregoing, a director, officer,

                                      -3-
<PAGE>
 
employee, or agent of the Corporation shall be able to contest any determination
that the director, officer, employee, or agent has not met the applicable
standard of conduct set forth in Sections 1 and 2 by petitioning a court of
appropriate jurisdiction.

     Section 5.  Expenses incurred by an officer or director in defending or
settling a civil or criminal action, suit or proceeding shall be paid by the
Corporation in advance of the final disposition of such action, suit or
proceeding upon receipt of an undertaking by or on behalf of such director or
officer to repay such amount if it shall ultimately be determined that he is not
entitled to be indemnified by the Corporation as authorized in this Article
VIII.  Such expenses incurred by other employees and agents shall be so paid
upon such terms and conditions, if any, as the Board of Directors deems
appropriate.

     Section 6.  The indemnification and advancement of expenses provided by, or
granted pursuant to, the other sections of this Article VIII shall not be deemed
exclusive of any other rights to which those seeking indemnification or
advancement of expenses may be entitled under any Bylaw, agreement, vote of
stockholders, or disinterested directors or otherwise, both as to action in his
official capacity and as to action in another capacity while holding such
office.

     Section 7.  The Corporation shall have the power to purchase and maintain
insurance on behalf of any person who is or was a director, officer, employee,
or agent of the Corporation, or is or was serving at the request of the
Corporation as a director, officer, employee, or agent of another corporation,
partnership, joint venture, trust, or other enterprise against any liability
asserted against him and incurred by him in any such capacity, or arising out of
his status as such, whether or not the Corporation would have the power to
indemnify him against such liability under the provisions of this Article VIII.

     Section 8.  For purposes of this Article VIII, references to the
"Corporation" shall include, in addition to the Corporation, any constituent
corporation (including any constituent of a constituent) absorbed in a
consolidation or merger which, if its separate existence had continued, would
have had power and authority to indemnify its directors, officers, employees, or
agents, so that any person who is or was a director, officer, employee, or agent
of such constituent corporation, or is or was serving at the request of such
constituent corporation as a director, officer, employee, or agent of another
corporation, partnership, joint venture, trust, or other enterprise, shall stand
in the same position under the provisions of this Article VIII with respect to
the Corporation as he would have with respect to such constituent corporation if
its separate existence had continued.

     Section 9.  For purposes of this Article VIII, references to "other
enterprises" shall include employee benefit plans; references to "fines" shall
include any excise taxes assessed on a person with respect to an employee
benefit plan; and references to "serving at the request of the Corporation"
shall include any service as a director, officer, employee, or agent of the
Corporation which imposes duties on, or involves services by, such director,
officer, employee, or agent with respect to an employee benefit plan, its
participants or beneficiaries; and a person who acted in good faith and in a
manner he reasonably believed to be in the interest of the participants and
beneficiaries

                                      -4-
<PAGE>
 
of an employee benefit plan shall be deemed to have acted in a manner "not
opposed to the best interests of the Corporation" as referred to in this Article
VIII.

     Section 10.  The indemnification and advancement of expenses provided by,
or granted pursuant to, this Article VIII shall, unless otherwise provided when
authorized or ratified, continue as to a person who has ceased to be a director,
officer, employee, or agent and shall inure to the benefit of the heirs,
executors and administrators of such a person.

                                   ARTICLE IX

                                     BYLAWS
                                     ------

     The Bylaws of the Corporation may be amended or repealed, or new Bylaws may
be adopted (i) by the Board of Directors of the Corporation at any duly held
meeting or pursuant to a written consent in lieu of such meeting or (ii) by the
holders of a majority of the shares represented at any duly held meeting of
stockholders, provided that notice of such proposed action shall have been
contained in the notice of any such meeting, or pursuant to a written consent
signed by the holders of a majority of the outstanding shares entitled to vote
thereon.


     The undersigned, being the incorporator hereinbefore named, for the purpose
of forming a corporation pursuant to the General Corporation Law of the State of
Delaware, does make this certificate, hereby declaring and certifying that this
is my act and deed and the facts herein stated are true, and accordingly I have
hereunto set my hand this the 10th day of May, 1996.



                                                /s/ Thomas M. Hart III
                                                ----------------------
                                                    Thomas M. Hart III

                                      -5-
<PAGE>
 
                            CERTIFICATE OF AMENDMENT
                                     OF THE
                          CERTIFICATE OF INCORPORATION
                                       OF
                              STX CHEMICALS CORP.

        STX Chemicals Corp., a corporation organized and existing under the laws
of the State of Delaware (the "Corporation"), hereby certifies that:

        1.  In lieu of a meeting and vote of directors, the Board of Directors
of the Corporation, by unanimous written consent filed with the minutes of
proceedings of the Board of Directors of the Corporation in accordance with the
provisions of Section 141(f) of the General Corporation Law of the State of
Delaware (the "DGCL"), adopted resolutions approving and declaring advisable the
amendment of Article I of the Certificate of Incorporation of the Corporation to
read in its entirety as follows:

                                   ARTICLE I

                                      Name
                                      ----

            The name of the corporation is "Sterling Chemicals, Inc." (the
     "Corporation").

        2.  In lieu of a meeting and vote of stockholders, the required
percentage of shares of stock have given written consent to said amendment, in
accordance with the provisions of Section 228 of the DGCL, and said written
consent has been filed with the Corporation.

        3.  Said amendment was duly adopted in accordance with the provisions of
Sections 141, 228 and 242 of the General Corporation Law of the State of
Delaware.

        In Witness Whereof, the Corporation has caused this certificate to be
signed this 21 day of August, 1996.

                                    STX Chemicals Corp.



                                    By: /s/ T. Hunter Nelson
                                        --------------------------------  
                                            T. Hunter Nelson, Vice President