Why Brewman Tank Do Acid Wash Passivation in Beer Brewing Equipment Manufacturing?

Why Brewman Tank Do Acid Wash Passivation in Beer Brewing Equipment Manufacturing? 

First What is Passivation?

Passivating is where a nitric acid solution removes the unwanted oxides leaving just chromium oxide.

According to ASTM A380, passivation is the removal of exogenous iron or iron compounds from 

the surface of stainless steel by means of a chemical dissolution, 

most typically by a treatment with an acid solution that will remove the surface contamination, 

but will not significantly affect the stainless steel itself. 

In addition, it also describes passivation as "the chemical treatment of stainless steel with a mild oxidant, 

such as a nitric acid solution, for the purpose of enhancing the spontaneous formation of the protective passive film.

Why Brewman Use Passivation?

Passivation is highly recommended by most everyone in the industry here 

(both brewers and chemical suppliers both).  

New brewing equipment gets passivated initially with a fairly-strong acid mix. 

Then each month or two thereafter, the equipment gets re-passivated with an acid mix slightly more diluted than the initially passivation. 

This process should rid the surface of any small rust spots or other vulnerable areas where oxygen can attack the stainless.

when welding joints or when the stainless steel is rolled in heat various oxides can form on surfaces. 

With stainless steel you will should get a consistent layer chromium oxide, 

that is why stainless is resistant to corrosion. 

If the stainless is exposed to any heavy contamination (like oils , excessive carbon etc.) 

during the forming or welding processes it can have other oxides form, mostly containing Iron and need passivating.

So how is passivation processing?

The process typically begins with a thorough cleaning cycle. It removes oils, greases, forming compounds, 

lubricants, coolants, cutting fluids and other undesirable organic and metallic 

residue left behind because of fabrication and machining processes.

The detail process is as follow:

First, inner tanks are finished

Second, filing the tanks with water to accelerate radiating and reduce carbonization .

Third, the dimple jacket is welded.

Four, Close or seal all the hole, sparging the acid to inner tank, and react 48h(Summer) or 36h(Winter)

Five, Open all the hole after acid reacting, tanks are cleaned by alkalescent water first and then cleaned by high pressure water.