How to remove ferrous contamination on Stainless Steel 2

[babouic]

Dear gents,
I'm working as an Anti-corrosion coating engineer, and I'm writting a Painting Specification.

We may have some stainless steel to protect with a two coats painting system (High build epoxy 2*200µm).
In order to properly apply this sytem we shall blast cleaned the surface with non-ferrous abrasive material (garnet, aluminium oxide...)
And before any paint application we have to be 100% sure that we don't have any ferrous contamination on the surface. We are using test to reveal any ferrous contamination (As per ASTM A380 §7.3.4)

My question is the following, as far as I understand the "prussian blue solution" (Distilled water, Nitric acid, Potassium ferricyanide) is only revealing the contamination, but I can't find any information on how to remove this contamination.

Is this solution is also able to remove the ferrous contamination ? If yes, what would be the procedure ?
Do you have any reference of cleaning kit from vendor ?

Cheers,
M.D

 

[EdStainless]

The cleaning process is called passivation.
ASTM A967 has some basic solutions that are proven for this application.


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[1gibson]

Probably want to specify use of only new abrasive.

 

[moltenmetal]

Pickling will remove contamination of all sorts, including free surface iron. Passivation is repairing and building the surface oxide film that actually protects the underlying metal. Some passivation processes also remove some types of contamination. If all you're after is surficial iron removal, citric acid will do it without the hazards of pickling paste or baths.

http://citrisurf.com/wave.htm

That's not an endorsement of their particular solution, it's just the first link I found in a Google search on the topic.

 

[EdStainless]

In stainless steel a passivation treatment is strictly a cleaning operation.
Letting the metal sit 72 hours in air will do more to build a passive corrosion resistant layer than any chemical treatment.
But for that to happen the surface needs to be clean.
Nitric acid is the traditional chemical used. Citric works, if it has some additives in it. It takes longer, but it is also much easier to work with.

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