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Immunity of steels
2.8.2023
DO YOU KNOW HOW ANTI-CORROSION PROPERTIES WORK IN AUSTENITE STEELS?
Very similar to human immunity. The degree of our defense against external influences (viruses, bacteria) is determined by the body's ability to repel these threats with the help of antibodies or cellular immunity. Austenitic steel has alloying elements, primarily chromium, instead of anti-antibodies. It creates a very weak layer of oxides on the surface of austenitic steel and thus prevents corrosion. Other elements, nickel and molybdenum, also increase corrosion resistance. Just as our immunity is not infinite and varies based on age, antibodies created, physical or mental state, austenitic steel has its types. Each type of steel has its typical material composition, and this defines the inertness of the surface to the formation of various types of corrosion.
Through the process of pickling and passivation, we rehabilitate this imaginary immunity of steel after previous weakening, for example, during material processing (welding, bending, grinding, etc.) and build up the pickling surface with the highest degree of inertness to corrosion that can be created for the given composition of the material.
Despite all this, this condition, this defensive ability of the material, can be broken down very quickly and external influences can be allowed to start corrosion instantly. You ask how?
In the photos below, you can find a typical example of a breach of the defensive passive layer using careless grinding with a regular carbon steel brush or other unsuitable material. If exposure to negative external influences is stronger than the protective layer of stainless steel, corrosion will always occur sooner or later. It is therefore very important, even after pickling and passivation, to ensure proper storage, handling of the material and, in case of damage to the passive layer, re-chemical treatment of the surface, which will rebuild the maximum possible immunity of the pickling surface.
Do you find it appropriate to compare the anti-corrosion properties of steel with human immunity?
Do you know what can be used to break the defenses of stainless steel?
Share your experience.
