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Non Alkali Metal Chromate Bath and Process

IP.com Disclosure Number: IPCOM000076998D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue


Related People

Owen, CJ: AUTHOR [+2]


A chromate protective coating is deposited on a base metal as follows:

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

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Non Alkali Metal Chromate Bath and Process

A chromate protective coating is deposited on a base metal as follows:

The base metal is immersed in a hot alkaline cleaner comprised of 60 gms/liter of trisodium phosphate, the base metal is then maintained in the cleaning solution for 2 minutes at a temperature of 170 degrees F. It is removed and rinsed in deionized water. The surface is then given a light acid etch by immersing in a solution containing 225 gms of ammonium persulfate per liter. It is rinsed again in the deionized water for 15 to 30 seconds. Thereafter, it is immersed in a chromate bath comprising: NH(4)Cl 5 to 20 gm/liter (NH(4))(2)Cr(2)O(7) 25 to 150 gm/liter NH(4)HSO(4) 2.5 to 25 gm/liter pH 1.0 to
2.5 - 60 to 100 degrees F operating temperature. Time variable to obtain desired film thickness, 15 sec. (for high-concentration bath) to 4 minutes (for low- concentration bath) being preferred. pH adjustment. Use NH(4)OH to raise pH. Use CrO(3) to lower pH.

It is then removed from the bath and rinsed in deionized water for 30 seconds and is forced-air dried. A preferred chromate bath composition is as follows: NH(4)Cl 10 gm/liter (NH(4))(2)Cr(2)O(7) 75 gm/liter NH(4)HSO(4) 10 gm/liter pH
1.5 time 3 min. - 75 degrees F.