What environment is not conducive to the storage of 303 stainless steel rods

The passivation of 303 stainless steel rods is also related to the characteristics of the medium, especially the oxidation capacity of the medium. In oxidizing media such as nitric acid, NO3 is oxidizing, 303 stainless steel rod surface oxide film is easy to form, passivation time is also short. In non-oxidizing media, such as dilute sulfuric acid, hydrochloric acid, organic acid, low oxygen content, passivation required time to be extended. When the oxygen content in the medium is low enough to a certain extent, the 303 stainless steel rod cannot be passivated. For example, in dilute sulfuric acid, the corrosion rate of chromium stainless steel is even faster than carbon steel. So must be based on the characteristics of the working medium to correctly choose the use of stainless steel.

For the atmosphere, water, water vapor and other weak corrosive media, as long as the chromium content in the solid solution w(Cr)>10%-12%, it is guaranteed to rust. In oxidizing acids such as nitric acid; Because there is enough oxygen to make stainless steel achieve passivation in the short term, but the acid contains H+ as a cathode depolarizer, so with the increase of H 10 concentration, the chromium content required for passivation also increases. Only in this way, the chromium content in the oxide film can be improved, and the oxide film with high chromium has good stability in nitric acid. Therefore, w(Cr) must be higher than 16% of the steel to have a high passivation ability. 2 sultry less. In dilute sulfuric acid and other non-oxidizing acids, because the medium dissolved in some oxygen is the lowest, and SO4 is not an oxidant,H+ concentration is high, the general 303 stainless steel rod and Cr18Ni9 stainless steel corrosion resistant steel is difficult to achieve passivation, so it is not corrosion resistant.

What environment is not conducive to the storage of 303 stainless steel bars

If the chromium content is increased, not only the corrosion resistance can not be improved, sometimes even reduced. In this type of medium, 303 stainless steel rod needs to add elements to improve the passivation ability of steel, such as nickel, silver, copper and so on. Hydrochloric acid is also a kind of non-oxidizing acid, stainless corrosion resistant steel in which is not corrosion resistant, generally need to use Ni-Mo. Alloy, so that the alloy surface to generate a stable MoOCl2 protective film, in order to maintain good passivation ability.

In the strong organic acid, due to the low oxygen content in the medium, and the presence of H+, the general chromium and chromium nickel stainless steel is difficult to ton. Molybdenum, copper, manganese and other elements must be added to the steel to improve the 303 stainless steel rod ton capacity, in the medium containing C1-, C1- easy to destroy the oxidation film on the surface of stainless steel, through and Angle with the steel surface, resulting in point corrosion. Stainless steel containing molybdenum enhances the ability of k - point corrosion.