Jump to content
ADI Forums
Hudson bay distillers

passivating stainless

Recommended Posts

hello everyone i was wondering if anyone has a method they are willing to share for passivating stainless steel other than nitric acid bath . need more of a spot treatment like welds ect not the entire vessels . any info is appreciated . thanks 

kim 

Share this post


Link to post
Share on other sites
Falling Rock    19

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...

Share this post


Link to post
Share on other sites

There is a company called Stellar solutions that makes a citric acid gel specifically for stainless passivation.  Citric is a lot safer to work with than nitric, and the gel is great for spot treatments because it stays put for a long time.

  • Like 1

Share this post


Link to post
Share on other sites
Foreshot    12

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.

Share this post


Link to post
Share on other sites
captnKB    19

Nitric is my preferred method to passivate stainless. @Hudson bay distillers im curious any reason for the aversion on using nitric to passivate?

Share this post


Link to post
Share on other sites

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 . 

Share this post


Link to post
Share on other sites
Streven    1

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. 

  • Like 1

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites
Natrat    3

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 :-)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×