A metallurgy guide for winemakers and brewers
Steel fermentation tanks, bubbles and vats are a wonderful invention, which, however, found many critics. As far as some of the allegations arise from the properties of steel, the vast majority is due to the fact, that buyers don't quite understand, what they really buy.
Steel of steel uneven
Steels are a very large group of alloys. In culinary applications, and therefore also in the production of homemade alcohol, stainless steels are the most widely used, which is a concept already confusing at this stage, for there is no steel, which will not rust. Noble steels, because that is how they should be defined in accordance with professional terminology, are a group of alloys, which, indeed, can rust, but the process takes a long time and requires specific conditions, and the resulting rusty coating is very easy to remove, to obtain a perfectly clean surface again.
Manufacturers of steel ladles and accessories use very different markings for their products. The problem is, that many times they are symbols taken from standards that are no longer in force or completely incomprehensible to laymen. Because every manufacturer tries to do everything, so that its products gain the largest market share, all this confusion with the markings is often used to introduce additional terms, which are completely irrelevant, but marketing is pretty good. Depending on this, what accessories you look at may be surgical steel (there is no such thing at all), low carbon (the carbon content in most types is less than 0,08%, and in the most common acid less than 0,03%, ennobled steel (it is also unknown, what that could mean) lub stainless (which means stainless in Polish, and that's an abuse, because all steel will rust).
What markings to look for?
The most popular and good quality cans or vats will be made of steel with the designation 18/10, 18/8, less often 18/0. These two numbers always represent the addition of chromium and nickel as a percentage. Chromium is responsible for protection against the effects of acids, and nickel adds hardness and delays rusting, however, it is one of the best known metallic allergens. The minimum amount of chromium in stainless steels is 16,5%, but it's a rarely used alloy. The greater the addition of chromium (and it can go as far as 1/5), the more resistant the steel.
This is the simplest marking model, however, you will often find others: AISI 304, i.e. standard stainless steel, the most used. It is a good quality steel, which is used practically everywhere, where the environment is not overly acidic, for example in the food industry. AISI steel is similar to the above 321 and various types of AISI 316, but the latter are intended rather for the production of items exposed to aggressive chemicals and high temperatures, therefore, as a material for the construction of barrels, kegs etc.. they are a bit like a fly cannon, but there are isolated cases of their use. The addition of titanium marked with the letters Ti or T in different types of symbols is not required - it reduces the risk of carbide formation, which in standard domestic conditions is still slim.
Each manufacturer will use markings on their products, whatever it deems appropriate, however, unfortunately most of them are completely useless, because they cannot be compared to any known standards. I hope, that the short cheat sheet on metallurgy and material technology presented in this article sheds some light on the matter and the next choice of a steel ladle will be dictated by its real advantages, and not the effectiveness of marketing efforts.