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Why passivate if part is plated?

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Current question:

December 2, 2021

Q. HELLO,

IS IT POSSIBLE TO PERFORM PASSIVATION METHOD 1 TYPE 2/6 OR 7 ON S.ST 302 BEFORE GOLD PLATING PER ASTM B488 [affil. link to spec at Techstreet]?
THANKS.

ALEX SHUSTER
- HAIFA, ISRAEL
^


"PASSIVATION AND CORROSION RESISTANCE OF STAINLESS STEEL"
by Milan Prazak
from Abe Books
or

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December 2021

A. Hi Alex. You cannot plate properly onto oxides, only raw active metal, so I'd say no -- but read on for second opinions.

Luck & Regards,

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


December 6, 2021

A. My understanding of this is that stainless steel does not receive plating very well, and must be activated (the opposite of passivation!) in order to do so. Therefore passivating stainless before sending it off to be plated would be wasted effort.

Never mind the question of why you would pay extra for stainless steel alloy only to cover it over. The only time that is justifiable to me is when the plating or coating is only partial, not the entire surface.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
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^




Closely related Q&A's, oldest first:

"ISO-16048"
Passivation of corrosion-resistant stainless-steel fasteners



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2002

Q. We manufacture solenoids & valves. The solenoid is made of C1215 ends and SS304 center. The parts are silver induction brazed. Some are machined on both the ID & OD. Some are only machined on the OD. They are electroless nickel plated. The plating process includes a Modified Woods strike. The question is: Why should the SS304 be passivated if it is to be electroless nickel plated? Why should any stainless steel be passivated if it is to be plated?

Paul Bryner
- St. George, Utah, USA
^


simultaneous 2002

A. Only reason that comes to my mind is to avoid stains or corrosion in the mean time they are plated. Passivation will have to be eliminated and parts be activated for plating to proceed.

Guillermo Marrufo
Monterrey, NL, Mexico
^


2002

A. I could be misunderstanding something, but I have to agree with you that it seems to make absolutely no sense. It's challenging enough to reliably activate stainless steel so that it can be successfully plated without deliberately passivating it first :-)

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


simultaneous 2002

A. We also get similar requests, stainless for passivate and black oxide or passivate and electropolish. I suppose the engineer who decided on these processes for their parts wants to ensure against any free iron that may be present from the machining stages of production.

Bill Grayson
- Santa Cruz, California, USA
^


2002

A. I get variations of this question all the time. Usually the question is about whether the passivation will affect adhesion of the plating. We have some customers who are passivating before plating "to get rid of any free iron on the surface". As stated above, this might be necessary if the parts are kept in inventory for a period of time in which the iron could rust prior to plating and begin a serious problem if left unattended. However, we see no reason other than this to passivate, since the activation process (made more difficult by the passivation) will take care of any surface problems prior to plating. When asked whether the passivation will affect adhesion we generally tell our customers that it will not help, but could adversely affect the adhesion of the plating. Bottom line- if you are plating immediately there should be no reason to passivate it first.

lee kremer
lee kremer sig
Lee Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois

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^


2003

A. I am somewhat in disagreement here. Why passivate first? Probably because the base material (stainless steel) was selected for its corrosion resistance. As such should the stainless steel not be in the most corrosion resistant condition? Just like painting over peeling paint plating over areas prone to anodic corrosion will not yield the best service life to a component. Passivate first to obtain a uniform surface for activation and further plating.

Jon Quirt
- Fridley, Minnesota
^

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