Few months ago, we got complain from Oman and Australia, said SinoBatoo mini kegs were made in carbon steel or iron, definitely not stainless steel, because when they took magnet close to our mini kegs, and it was attached!
Apr 13th, 2018, our Korea distributor NaRiS Solution asked “Why 2L mini keg and growler are stick to magnet?”
Were SinoBatoo mini kegs made of stainless steel 304? Why it can attach magnet? To find the answer, one of our distributors (Beerkat Australia) took several SinoBatoo mini kegs to local lab and requested for physics testing. The lab tester took Bruker portable Alloy Tester closed to surface of mini kegs, and took few minutes got testing report:
From the test report, it shows all mini kegs were made in stainless steel 304, the constituent of Chromium (Cr), Manganese (Mn) and Nickel (Ni) percentage are within the standard range.
Why steel is stainless 304 has magnetic?
It is a common mistake to judge stainless steel or carbon steel by magnetic. Alessandro Fais, BD and MS in Materials Eng., PHD in Metallurgical Engineering published a blog on May 25 2017, mentioned “Of the three great families of stainless steels available (martensitic, austenitic and ferritic) two are attracted by magnets: the martensitic and the ferritic ones. I am purposefully ignoring mixed grades (ferritic-austenitic and so on) since they are all blandly attracted by magnets. The only group which is not ferromagnetic is the austenitic one. ”
Meanwhile, for austenite stainless steel, the raw material is without magnetic, but during process, the molecular structure would be changed, especially for mini keg, there are several steps, such as hydro forming and stretching, spin forming, those processes would break the original structure of steel.
To clean inside of mini keg, we are using magnetic needle to polish, the magnetic needle would pass the magnetic to mini keg too, and that’s why SinoBatoo mini kegs were being attracted by magnet weakly.
Next question: Why there are rust points on mini keg lid or keg body?
When you finished a keg beer, you will wash the mini keg and dry it by putting in kitchen or dinner table, buy somehow you would find there are few rust on the surface, why?
The reason is there are unclean impurities on surface of mini keg lid or body, if the condition is moist, the vapor will attach to impurities and get rust point. This is very common appearance, by carefully cleaning, you would easy to remove the surface impurities and rust, to get back a shinning mini keg, but remember, don’t use hard metal brush to wash the mini keg.