Pickling & Passivation

equipment used in sanitary environment such as food processing, as the dairy industry. It has to be passivated, and this is done with is acid. Nitric acid is usually used and usually at higher strength, the % of acid I do not have at the moment.

Soap and water will not do it. There is chemistry involved. basically, BUT NOT THIS SIMPLY, Alkaline removes proteins. Acid removes minerals. Any proteins left on the surface when you run acid, and it will basically embed into the stainless. Passivation is difficult and dangerous, and only should be done by trained personal. But it has to be done to meet some sanitary standards.

Also at the shipyards, we had to pickle the aluminuim parts prior to installation to ensure clean welds. And if a certain number of days past after pickling and its not welded in yet. they have to be pickled again.

p911

It is a bit more complicated than just improper segregation.

If environmental concerns are an issue try Citric Acid.

We have been using it for a time with great success.

Here is what is being used at present.

http://www.citrisurf.com/wave.htm

Good answer with both of the queries answered.

Since a lot of SS has been produced in my part of the world and to date many fabricators don't understand segregation, contamination, pickling, and passivation, it has been very informative to visit a few of the producers of SS products.

Being at and seeing the pickling tanks at a local SS tube manufacturer surely gives one an understanding of the acids used for this process.

Having my vendors use citric acid has also solved some thorny disposal issues, even if it does take longer.

GA and explianation

What is wrong with greening the stainless? This is the process that I have done for this type of issue.

Greening: wet reduction at 750'C, N2/H2 gass.

Hi,

Pickling is the process to removing the oxidation layer of welding as well as ss surface, if your not remove the oxidation it will start corrode, may not be immediate but after some time,so pickling is must especially on welding and may not required in other area depends up on the usage.

Passivation is the process to neutralise the pickling process other wise pickling acid ( nitric ) will react with the base material and it will eat the base material after some time.

Shot blasting is the process to improve the fatic strength of materials and it will give cleaned surface for welding as well as painting.so, pickling and shot/sand blasting are not for same purpose.

-Mayil,Hosur,TN

Thanks all for there contact

I would like to know, I should do both pickling & passivation?, by the way our tank will use for (corrossion inhibitor chemical) & (viscosity reducer chemical). I mean can I do only pickling?