The transformation of stainless steel balls is also rel […]
The transformation of stainless steel balls is also related to the characteristics of the medium, especially the oxidation ability of the medium. In the oxidizing medium such as nitric acid, NO3 is oxidizing, the oxide film on the surface of the stainless steel ball is easy to form, and the transformation time is short. In non-oxidizing media, such as dilute sulfuric acid, hydrochloric acid, organic glue. The oxygen content is low, and the time required for passivation must be prolonged. When the oxygen content in the medium is low to a certain level, the stainless steel balls cannot be transformed. For example, in dilute sulfuric acid, the corrosion rate of chromium stainless steel balls is even faster than that of carbon steel. Therefore, the stainless steel grades must be correctly selected and used according to the characteristics of the working medium.
For weak corrosive media such as atmosphere, water, steam, etc., as long as the chromium content in the solid solution w(cr)10%-12%, it is guaranteed not to be rusty.
In oxidizing acid such as nitric acid, because there is enough oxygen to make stainless corrosion-resistant steel reach a passivation state in a short time, but the acid contains hydrogen ions as a cathode depolarizing agent, so as the concentration of hydrogen ions increases, the passivation The required chromium content should also be increased. Only in this way, the chromium content in the oxide film can be increased, and the oxide film containing high chromium has good stability in nitric acid. Therefore, if w(cr)>10%-12%, no rust is guaranteed.