free acid test 1

[cmwatson78]

Why would someone do a free acid test on phoshate? What is a free acid test? What happens in the reacion and what web site can I go to, so I can get more info on determination of free acid using a sulfuric acid titration.

 

[kenvlach]

"Why would someone do a free acid test on phoshate?"
-- I think you mean, a test for free acid in a phosphating solution. Phosphating baths include phosphoric acid which reacts with the metal being treated Thus, phosphate is a neutralization product of this reaaction. The remaining free acid concentration can be determined by a simple titration to pH 4.5 using 1 [N NaOH solution. Total acidity is determined by titrating to pH 9.5.
Alternatively, each phosphating bath has an optimum pH range, and the pH can be measured directly.

"determination of free acid using a sulfuric acid titration"
-- This is confusing. Sulfuric acid can be used as a titrant to determine free NaOH (e.g., in caustic etches). NaOH can be used as a titrant to determine free sulfuric acid (as in sulfuric acid anodizing solution).

Please clarify. And, do you have a chemist or technician to do titrations?

 

[cmwatson78]

yes, the sad thing is I was hired as the "chemist" but when you have not used it for 4 years, you tend to forget.
its called the free acid test. it would be using sulfuric as the titrant of phosphate. using Parker Amchem as the indicator.
what I would like to know is what are they trying to indicate with the test. pH? plus, im new to this forum thing so if im doing something wrong, im sorry.
we do determine the concentration by titrating with NaOH.
plus, is Parker Amchem indicator #2 the same as Bromocresol Green .2% Aq.

 

[kenvlach]

Solution maintenance and titration procedures are given in MIL-HDBK-205A PHOSPHATIZING AND BLACK OXIDE COATING OF FERROUS METALS.

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=53933

I'm not sure about the indicator. You may be able to figure it out by comparing your reagents & titration procedures with those on pages 45-47 in MIL-HDBK-205A.
Parker Amchem was bought by Novamax was bought by Henkel.

http://www.henkelsurftechna.com/

In any case, if using a proprietary product, the vendor should supply the product bulletins, MSDS, etc.