Thread: Alternatives to stainless acid pickles

Originally Posted by Graziano

I looked up stainless passivation earlier this year and found an article that said to use 30% nitric acid in water. It made the steel shot blasted 316 that had gone tea brown after a day in the rain, go silver white in appearance and it's been fine for the last 5 months or so. I did several coats and rinsed off in between with the hose so the it didn't dry out with acid on it. Nitric is an oxidising acid apparently.

Nitric acid is only the first step as far as I am aware although there are some occasions when it is all that is able to be used. We had some 90 and 45kl tanks at work that were staining and these were treated by cleaning with nitric acid. It was a warranty job. The whole area was flagged off. I was asked if I wanted the drums the nitric acid came in last year as a big cleanup was happening. When I had a look at them I said why not. I was neutralising them anyway. They are a 20l and a 25l normal oil type drum but made of stainless steel! We also had some rotary fermenters which came from France as deck cargo on a ship. As they were not covered they received salt spray on the outside surface. These also had to be treated the same way.

I think I have some nitric acid. I might give it a try and see what happens.

Dean