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How about citric acid or even lemon juice? There are marine companies on the Gulf Coast using citric acid because the EPA cannot stop them from dropping lemon juice on SS ship parts and railings and washing it into the ocean...and it works.  Google it...

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  • 2 weeks later...

A lightly wet paper towel will stick to most things, even upside down, and will stay wet for a while. Load it up with a citric solution and let that sit for a bit. Or put a magnet on the opposite side of the still wall and then wrap another magnet or piece of iron/steel in a plastic bag. Use wrapped metal to hold the paper towel in between the bag and where you want the SS treated. If it is a big spot then this hillbilly method probably won't work.

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Confirming what others have shared.  Citric acid "wipe passivation" is all you would need.  We own a contract manufacturing business for medical devices (spine and ortho surgery instrumentation and implants).  The passivation spec all of our customers use is ASTM A967.  This allows for citric or nitric passivation.  Our customers and ISO 13485 require all of our "special processes" (which includes passivation) to be validated, so we have done all of the boil and copper sulfate testing on coupons that have been wipe passivated with citric (which is literally a thousand pages of documentation and who knows how many hundreds of coupons tested).  Anyone working in ISO environments knows IQ, OQ, PQ.....blah blah blah.   

All of our instruments are wipe passivated after laser or tig welding.  We wipe on, let sit for a couple minutes then wipe away with rubbing alcohol.  We use a product called CitriSurf 2250 Gel.  We avoid nitric at our facility just because of the added EPA regulations.  

I figure if it's good enough for the FDA and sterile instruments being used in the OR, should work for your application!  Happy passivating. 

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4 hours ago, Hudson bay distillers said:

thanks guy s for the tips i ll give it a try , i ordered a tig brush while i wait for it i ll try it . 

captain only plus i see to citric is easier to get and easier to dispose of , the tig brush uses phosphoric acid to clean and passivate   . when you use nitric are you soaking in acid bath or spot treating . 

We use a TIG brush here at TCW for cleaning and passivating TIG welds. Ours is the Capital Weld Cleaner. It works great for us. It's very quick and effective, but unless you're doing a ton of cleaning/passivating it sounds like what Streven proposes would be more simple.

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  • 2 weeks later...

All good solutions, but if you don't want to buy anything, most of us have citric acid powder sitting around. Mix into a paste, and apply to weld. Wait a few minutes and rinse. I find the wet paste works just like gel. Great for repairs around the shop :-)

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