QQP-35C Passivation Treatments For Corrosion Resistant Steel Q&A's about

A. We have been using an electropolishing process and achieving great results.

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Thanks, John, I have many times seen references to electropolishing being a better passivation process than passivation itself.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Ricks,

As John and Ted said, electropolishing is an effective method for improving the corrosion resistance of stainless steels. According to my experience, pulsely anodized stainless steels in mixed acids can pass the test with respect to ASTM B117.

A. Dear Ricks Lam:

Several Organic finishes will provide in excess of 2000 hours salt spray testing on mild steel. I'm certain these coatings would provide adequate protection on stainless steel as well.

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Ed. note: We advise with sadness that Mr. Schachameyer, a former AESF President, has since passed away.

A. To: Steve

QQ-P-35C allows a maximum of 7.5 grams / liter iron (Fe) for Type II and Type IV solutions. The maximum allowable interval for checking this is three (3) months. MMA monitors iron (Fe), chromium (Cr) and copper (Cu) content monthly, both to meet the specification requirements, and to ensure proper disposal of the acid when required. The most cost effective method of reducing the contamination content is dilution with new acid solution. If possible, siphon approximately 25 % of the tank from the bottom, much like you would clean an aquarium, and replace with fresh acid.

A. Hi David, this probably requires electropolishing rather than dipping in a passivation solution. Please read on ...

Regards,

"Electroplating Engineering Handbook"
by Larry Durney

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A. Hi Kevin,

Please see if you can get your hands on a copy of the Electroplating Engineering Handbook, which has an excellent chapter on electropolishing, and which will also introduce you to details about the related equipment

I don't think anybody can or will design an electropolishing plant for you for free via casual public responses here. You may wish to hire a consult in this field (some are listed at www.finishing.com/consultants and others may respond to your inquiry when they see it here), or you can ask equipment vendors (www.finishing.com/equipment) to quote you what they think you need.

adv.
Metal Coating Process Corporation is a specialist in this field, and conducts training sessions in electropolishing.

Good luck!

A. Electropolishing of 300 series shall hold good after doing electropolishing. The process is degrease -- rinse well -- dip in 5% phosphoric acid and load to electropolishing anode bus bar with 100% pure lead sheets as cathodes fully covering on either side. Electrolyte consists of Phosphoric acid 85% concentrate and sulfuric acid 1.84 specific gravity. YOU have to add 50% sulfuric acid and 50% phosphoric acid equally mixed in concentrated form -- be sure not to add anything including DM water. Now electrolyze keeping SS job as anode in titanium jigs. Voltage 4 to 7 volts and amperage depends on area of job. Time 2 to 3 minutes depending on area of job loaded. After electropolishing the job has to be rinsed in DM water and then dipped in chromic acid solution 250 grams per litre of DM water to remove the viscous film and to be super bright forever. Finally wipe off in yellow silver oak saw dust for best finish.

A. QQ-P-35C [from DLA] is cancelled, Frank. But you may wish to use it's replacement, ASTM A967.

Although some people sometimes must work to such "dead" specs, it's a good idea to try to change them because even if it is found that there is something flagrantly wrong with the dead spec, no mechanism exists to change it :-)

A. You can contact [finishing.com's supporting advertiser] Lee Kremer at Stellar Solutions [a finishing.com supporting advertiser] for whatever type of citric acid you may require. See ya'...