Passivate 316 stainless

Karl_T said:
need to make a weldament out of 316.

found I should use 316L:
alliantmetals.com

What’s the Difference Between 316 and 316L Stainless Steel? - Alliant Metals Inc.

There are quite a few varieties of stainless steel available for your production needs. If you’re new to selecting steels, then it might be confusing to tell the difference between them. We’ll take a look at two similar stainless steels, 316 and 316L, and explain the difference, so you know what...
alliantmetals.com

Plan to TIG it. any other special weld instructions?

Need to passivate also, never done this or anything like it. read this:
https://www.carpentertechnology.com/blog/how-to-passivate-stainless-steel-parts

This table is the meat of the discussion. No such thing as easy to buy nitric any more.

View attachment 470418


Found this on Amazon:

So, is 10% just this offer above 10% in water???

Need to heat to 150, can I just do this on an old stove in a restaurant food grade SS pan?

Other things I need to know??
Click to expand...
Buy a new lead acid battery and tell them you'll put the acid in it when you are ready to use it..... Nitric acid...
 
ddickey said:
I thought the L meant low, as in low carbon.
Click to expand...
Yes, it does. This is what makes 309L and 316L frequently suitable for welding high-carbon steels and sometimes cast iron. The dilution of the base metal with low carbon filler reduces the carbon content in the weld to the point where the weld doesn't become brittle on cooling. This doesn't always work, but has every time I've tried it, and is much cheaper than nickel or other specialty fillers.
 
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I worked in a sulfuric acid plant for 9 years everything including bolts, supports, brackets, and pipes were 316L, although I wasn't a welder, the welders never passivated any of the SS joints. most of the joints were stick welded with 316L rod. On critical joints TIG welding with a nitrogen backing gas was used. The only exception was the pipes used for the hydrogen peroxide circuit they were PVC. SS would corrode. The hydrogen peroxide would also burn leather gloves in seconds( it attacks anything organic)
All the SS piping in the plant had cathodic protection, this could be why passivating was never used, I don't know for sure though.
 
aliva said:
I worked in a sulfuric acid plant for 9 years everything including bolts, supports, brackets, and pipes were 316L, although I wasn't a welder, the welders never passivated any of the SS joints. most of the joints were stick welded with 316L rod. On critical joints TIG welding with a nitrogen backing gas was used. The only exception was the pipes used for the hydrogen peroxide circuit they were PVC. SS would corrode. The hydrogen peroxide would also burn leather gloves in seconds( it attacks anything organic)
All the SS piping in the plant had cathodic protection, this could be why passivating was never used, I don't know for sure though.
Click to expand...
When I worked at BAT we built peroxide concentrater and storage systems out of 316L SS and passivated it with nitric and HF acid, we were usi ng 5254 aluminum tanks with 1020 Aluminum nozzles. You were not likely dealing with the concentration we were using though. When FMC and Degussa met with us and we told them what we were doing they said we were crazy and we would kill a bunch of people, they were the experts and they were wrong.
 
The drawings I work to require passivation post machining. We have 2 heated ultrasonic sinks. First is sodium hydroxide (high PH) primarily as a degreaser. water rinse and then into either a citrisurf or citric acid tank that removes the free iron on the surface. I prefer the citric acid. Just be mindful of the dust when poured.
 
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