How much do you know about the corrosion resistance of stainless steel welded pipe?

Stainless steel welded pipe stainless steel stainless steel stainless steel and corrosion resistance refers to its resistance to suffer corrosion of the surrounding environment, or the degree of retardation produced by its corrosion, referred to as passivation.

From the chemical theory explanation

That stainless steel so corrosion resistance, because of its role in the media, the surface will have a layer of Cr20, the main film, that is, passivation film, the film is characterized by a very thin, in the chromium content of more than 10.5% of the conditions, generally only a few microns; the specific gravity of this film is greater than the specific gravity of the metal substrate, indicating that the film is very dense, so the film is difficult to be corrosive media penetration, thus effectively protecting the metal substrate not to be corroded. Be corroded.

Explanation from the electronic theory

The passivation state of the metal is considered to be related to the unfilled electron layer, in the iron-chromium alloy of stainless steel, stainless steel welded pipe prices, as chromium seeks to absorb electrons, so that the iron (Fe) atoms lose electrons and are passivated. Other scholars believe that when the amount of chromium in the solid solution of iron-chromium alloys up to 1 / 8 (i.e., 12.5%), its electrode potential can be increased to +0.2V from a 0.56V jump, the electrode potential increase, so that the metal in the electrolyte is more stable, that is, not easy to be corroded.

The above theories are based on the role of chromium. In fact, due to the diversity and complexity of the environment in which the material is located, under certain conditions also need to add other alloying elements to improve and consolidate the corrosion resistance of the material, such as the addition of key (Mo) elements, will make the corrosion product M002 a close to the substrate and promote the passivation of the substrate; the addition of copper (Cu) elements, so that the stainless steel surface passivation film contains Cu0, which does not play a role in the corrosive medium, thereby increasing the corrosion resistance of materials; addition of copper (Cu) elements, so that the surface of the passivation film contains Cu0, which do not play a role in corrosion, thereby increasing the material Corrosion resistance; add nitrogen (N) elements, will be enriched in the passivation film Cr2N, so that the concentration of chromium in the passivation film to improve the corrosion resistance of the material.

It should be noted that the corrosion resistance of stainless steel welded pipe is conditional. Medium type, concentration, temperature, pressure, flow rate and other differences in various factors on the corrosion effect of stainless steel is different, so the stainless steel stainless steel is relative. This point must cause our attention.