Stainless steel is mostly preferred over other kinds of materials because it can resist corrosion in rough environments although it is not fully resistant to rust/corrosion. Since it is somewhat resistant to corrosion, hence the name, stainless steel.
When stainless steel comes in contact with corrosive fluids or high humidity/high salinity conditions, the topmost layer of chromium oxide that protects the steel from getting corroded gets thinner and thinner with time which can cause the stainless steel screw to rust. Rust is not just bad because it looks unpleasant to the eyes but it also weakens the structural integrity of the instrument thereby affecting the overall performance and lifespan of the structure.
The topmost layer of steel that protects it from corrosion can only work if the concentration of chromium is at least 12%. Anything less than that causes the layer to weaken and thus the steel becomes prone to corrosion. Of the 5o grades of stainless steel that exist, some are more prone to rust and others are not. The grade and how much the stainless steel is prone to corrosion depends on the amount of chromium that has been deposited on it and the addition of other elements to the mixture. There can be many causes that may be the reason for the thinning of the chromium layer and eventual rusting of the stainless steel but the most common of the reasons include contact with hydrochloric acid, iron or carbon steel, sulfuric acid, and the environment is extremely temperature:
The chromium oxide layer that is supposed to protect the stainless steel screw from corrosion is extremely unsafe around chlorides. That is the reason why saltwater causes so much damage to stainless steel and that the instruments/machinery used in food and chemical industries have such a high amount of chromium content.
Same as chlorides, highly acidic substances too destabilize the layer on stainless steel making it defenseless against corrosion. Hydrochloric acid, sulfuric acid are some of the most strong acids and have the potential of harming stainless steel.
Iron and carbon steel particles
The chromium layer can also be damaged by coming in contact with iron and carbon steel particles that stick to the surface and cause the layer to break away slowly. This is why they need to be cleaned now and then. If left uncleaned the particles can cause the stainless steel screw to be more prone to corrosion because of the particles from welding, drilling, cutting, etc., of carbon steel nearby.
Getting exposed to extremely high temperatures can also be a cause for stainless steel to corrode although this is not such a common reason for rusting to occur. The reason why this is so rare is that steel rarely gets exposed to temperatures from 750F degrees to 1550F degrees. This can happen in cases where the steel is made hot and then rapidly cooled down. The heat makes the chromium oxide layer discontinuous, a phenomenon that is known as heat sensitization and can be detrimental to the quality of the stainless steel.
How To Take Care of Stainless Steel
Stainless steel is a very strong and durable substance that can last years if maintained and looked after properly. The best ways to keep it healthy are:
- Wear clean gloves when working with stainless steel
- Use components that are made of stainless steel as well
- Keep away carbon steels and iron
- Keep away concrete detergents
- Chloride solutions, bleach should be avoided
- Never use steel wool for cleaning
As mentioned earlier, regular cleaning and maintenance are important for the longevity of stainless steel. It must be cleaned regularly not just so that it looks clean but also because it is required for its health. With the right care, stainless steel will last you for years without getting corroded or rusting. Here are some things that one must keep in mind while cleaning:
- Regularity - it should be cleaned every 6 months or so.
- Soft brushes, like a nylon brush, should be used to wipe dust if any.
- Mild soap and detergents should be used to not damage the Chromium layer.
- The whole procedure should be followed by a rinse with clean water.
- The surface should be cleaned dry with a soft cloth or an air blower.
These are all the things one needs to know, apart from all this one also must the instructions, if any, and keep them in mind. Also while working with these things one must wear protective gear such as gloves, glasses, etc.