There are several types of stainless steels - open-hearth, austenitic, ferritic or mixed. Their common property is resistance to atmospheric air and aggressive environments. They are made of stainless steel, including household items, so the need to distinguish it from other grades of steel may arise at home.
It is necessary
- - magnet;
- - alkali solution (sodium or potassium hydroxide);
- - concentrated nitric acid;
- - chemical vessels;
- - laboratory pipette;
- - vinegar;
- - soda;
- - file;
- - solvent;
- - rags.
Any steel is an iron alloy. In order to determine if iron is included in the material at all, take a permanent magnet. A magnet is attracted to an object made of an iron alloy. If this does not happen, then the thing is made of some other material. Outwardly, titanium is most similar to stainless steel, but there may be an aluminum alloy. You can also distinguish it from titanium by weight, it is much heavier.
React with alkali. If you are dealing with steel filings, then pour lye into a test tube, and then dip some sawdust there. Use a pipette to drop some alkali onto a steel sheet or dish. Stainless steel, unlike aluminum alloys, does not react with alkalis. Brown rusty spots of iron hydroxide form on the surface of ordinary steel. It is necessary to take a laboratory pipette, which is a glass tube, which is clamped with a finger from the upper open end. A medical pipette will not work because acid or alkali will corrode the rubber.
Experiment with acid. Carry out the reaction in the same way as with alkali. It is best to take concentrated nitric or sulfuric acid. Conventional steels are stepped with acid into an active reaction with the evolution of hydrogen. Stainless steel does not react with this group of substances, because it contains alloying additives. They are inhibitors of this reaction. Chromium, vanadium and other substances are used as such additives.
If you have a large piece of metal, it becomes necessary to make sure that it is all stainless steel, not just the coating. Use a file or sandpaper to clean the area, removing the top layer of metal from it. Then react with acid and alkali.