finishing.com -- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing

HomeFAQsBooksHelpWantedAdvertiseForum
topic 049

Passivating 316 SS

adv.   stellar solutions banner

(1995)

Q. We recently got an order in from one of our regular customers and the paper work called out zinc barrel plate w/ yellow chromate. Which we did in an alkaline zinc and to my amazement I later found out that these parts were 316 SS and should have been passivated instead of plated.

My first question is why did these 316 SS parts zinc plate as well or better than the same parts do in steel? And my real problem is when I stripped the zinc off and go to passivate them they form a brownish green smut on the parts that will not come off in the nitric passivation solution. Any Ideas?

Paul P [last name deleted for privacy by Editor]


(1995)

A. Paul: Here is a reply to your question by Max Stein, who has been doing alkaline zinc plating for many years:

"Zinc oxide: Alkaline zinc plating solutions are famous for co-depositing a matrix of Zinc oxide within the metallic Zinc. Most probably, that is what it is. Right, it must normally be white, but when talking about very small particles... (As plated, coating from alkaline zinc are often yellowish to brownish-green: due to the same phenomena). It is not easily dissolved neither in hydrochloric nor nitric acid. Reprocessing through alkaline clean - hydrochloric acid - scale conditioner (hot caustic with potassium permanganate: often used in passivation pre-cycle on heat treated CRES) will definitely help.

Another option - concentrated chromic/nitric acid mix. It must be interesting to see if you have obtained a reasonable degree of adhesion: bend or file test can be done. If adhesion is very good (which I doubt very much), you may have developed a new method of activating CRES. Cheers, Max"

berl stein
berl sig
"PlaterB" Berl Stein
NiCoForm, Inc.
supporting advertiser
Rochester, New York

nicoform


(1995)

A. Sometimes SST will plate just fine without a nickel strike. I never could figure out why. As for the smut after stripping zinc, try soaking for 3 minutes in a spent (or new) cyanide based nickel stripper (room temp).

Ken Rosenblum
finishing shop - Minneapolis, Minnesota


(1995)

A. Paul, you are really putting your plow into new ground, I have never heard of anything like this before, and I am fascinated. I would like to take a look at the problem, and do some research work to try to determine what is going on, and how to resolve the issue. If you send me parts, I will do the work, and report to you on what results we got.

Rudy Sedlak
Mountainview, California



This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Q or A to THIS thread START a NEW THREADView This Week's HOT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices


©1995-2017 finishing.com     -    Privacy Policy
How Google uses data when you visit this site.