Arch Chemicals (ARJ) 10-Q 2004 Q2 Quarterly report

Exhibit 32.2

CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER

PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Arch Chemicals, Inc. (the “Company”) on Form 10-Q for the period ending June 30, 2004 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Louis S. Massimo, Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that to my knowledge:

(1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of and for the periods presented in the Report.

The foregoing certification is provided solely for purposes of complying with the provisions of Section 906 of the Sarbanes-Oxley Act of 2002 and is not intended to be used or relied upon for any other purpose.

/s/ Louis S. Massimo

Louis S. Massimo

Chief Financial Officer

August5, 2004

A signed original of this written statement required by Section 906 has been provided to Arch Chemicals, Inc. and will be retained by Arch Chemicals, Inc. and furnished to the Securities and Exchange Commission or its staff upon request.