Stainless Steel Pickling ?
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    Default Stainless Steel Pickling ?

    I have recently silver brazed some delicate assemblies of 316 stainless and hypodermic tubing. In the past I have pickled similar brazements in stuff called Sparex which is a common jewelers pickling compound but wonder if thee is something better for stainless steel. The Sparex is sold in granular form and dissolved in water and then kept warm in a small crock pot. I do have muriatic acid, some sulphuric acid and maybe some nitric acid on hand. I wonder about citric acid and maybe even acetic acid (vinegar) as possible pickles. What do folks suggest? Thanks for any useful replies!

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    Look up "passivate" for stainless. Among a great many other things, citric acid has been used for small-shop low-hazard passivation.

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    Something to consider is after brazing, (unlike after welding), you are dissolving flux as a big part of the clean up, so the proprietary “weld cleaners”, the passivating solutions, and other post-weld cleaning procedures and processes are going to come up short.

    Warm sodium bisulfate solution (spearex) is hard to beat for that. After pickling, one of the other processes could be used to further clean and passivate, but if it is for medical, I’d think it would go to an electropolish anyway.

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    For small stuff like that I've used a mix of a little nitric with hcl for diy picking. For just passivating I've used straight hcl, just don't leave it in either too long, it will turn black and ruin your parts, keep an eye on it. Once the surface gets a dulled, matte finish I pull out.

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    Excellent info - thanks!

    I typically boil them in water post brazing to dissolve the flux but I need something to remove the oxide layer. So a pickle bath is next, some polishing with rouge and then ultrasonically clean them. Muriatic is HCL correct?

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    commercially, stainless passivating and polishing is done with phosphoric acid. its a lot less dangerous than sulfuric or HCL or nitric. It works fine.
    Job site stainless cleanup has been done by electropolishing with citric acid for decades now.
    Again, less likely to burn thru to your bones, or even leave holes in your jeans.

    CitriSurf Citric Acid Passivation | Stellar Solutions - Stainless Steel Passivation

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    Quote Originally Posted by Gazz View Post
    Excellent info - thanks!

    I typically boil them in water post brazing to dissolve the flux but I need something to remove the oxide layer. So a pickle bath is next, some polishing with rouge and then ultrasonically clean them. Muriatic is HCL correct?
    “Muriatic” is bull, and should be tossed out with the lead paint and the uranium glazes and the X-ray foot measuring rigs, yes, it is hydrochloric acid, and that and the wolmanized lumber and the Nirod gets you absolutely nothing.. pass me the Kleenex and get yourself a Tampex..

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