It is quite a nuisance to either a winery or a brewery when facing the problem of rusts to a stainless steel wine tank or beer tank because hygienic is always the top concern for food.
You would think that stainless steel tanks never actually stain but it does, sometimes. To understand what makes stainless steel rust it is first important to understand the science that typically prevents it from rusting. Stainless Steel is a combination of Iron, Nickel Chromium and a few other chemical elements which react with oxygen from water and air to form a very thin, stable film that consists of such corrosion products as metal oxides and hydroxides.
Once this special film is destroyed, the stainless steel will go rusting. Rust is nothing but oxidation of Iron. Let us look at the may happen situations to the tanks in use.
1. Rusts are caused by contamination of the surface by contact with ordinary steel (external contamination)
The photograph shows rusts on lugs of a stainless steel tank due to the use of a carbon steel rope when lifting the tank.
This picture demonstrates how, (when little care is, taken) producing a side entry door for a wine tank, using iron rich articles of tooling, can be introduced into the stainless. Without exception, material containing iron should be kept a minimum of 12 meters clear of this any stainless.
2. The welded or polished surface is not properly passivated
Passivation is a must do step to restore or enhance the chromium oxide film on the stainless steel surface when it has been manipulated by surface finishing, welding or grinding.
This picture shows the rust spots on a top entry lid for a wine storage tank when passivation is not done to the welding areas.
3. Chloride attach on stainless steel tank surface
Chloride is an excellent rust cause with a little damp air moisture. High chlorine content of the water during cleaning process will easily make the tanks stain.
Copyright Statement: It is the original works of INTECHWELL and is protected by copyright. Copying of this article is permitted (with permission from the author), but this must be clearly indicated in the article and the original link must be presented.
Contact us to learn more.