[toniasmall]

I work for a Centrifuge company and we deal with alot of stainless steel. We want to build some vats for cleaning the stainless steel. I was told that nitric acid was "stainless steel friendly" and would remove the hydrocarbons from it. Would nitric acid be what I would need to put in the vats to clean the stainless steel? If so, do I need permits to purchase this?

[enahs]

If you use semi dilute nitric acid it should not be too much of a problem. But if you use concentrated nitric acid for long periods of time or even semi dilute but with heat you can have serious problems. It depends on a lot on the stainless steel type, and what other ions are in solution (so depending on what you might be cleaning off, etc). Sometimes even dilute cold conditions CAN have a serious effect.

Honestly, I find that the best way to clean stainless steel is to take some finely powdered alumina (very cheap) and put very little water on it and make a paste, and then just use it and a thick paper towel or so and scrub it off. This is really just a polishing technique, but works better then anything I have ever found. And I clean a lot of stainless steel. There is more manual labor involved though.

On a large scale, just a polishing wheel on the end of a drill with the paste might be high throughput enough.

[mc_75]

I usually clean the reactors and the heat exchanger of my plant with a 6-8% solution of nitric acid.

the solution flows in the pipes and in the reactors for about three hours at about 80°C. this permits the discale of organic residuals formed during an oxidation at 300°C.
pay attention that the solution is every time clean: only nitric acid and potable water.