The principle of corrosion resistance of stainless steel pipes for water

In modern household water supply pipes, the corrosion resistance of water pipes is very important, because it means we can drink healthy and pollution-free drinking water. When PPR plastic pipes were promoted as tap water pipes, a test report from the Shanghai Disease Research Institute showed that the total number of bacteria in the water quality of household PPR tap water pipes was countless, exceeding the banned galvanized pipes. Moreover, after severe corrosion inside the water pipe, when the water flow velocity at the end of the pipe network is low, if the water flow velocity in the pipe suddenly increases, it will easily cause the water flowing out of the water pipe to become turbid and yellow.

Therefore, countries such as the water industry, hospitals, food factories, and beverage factories now have to use stainless steel pipes. Commonly used stainless steels include 304 and 316 stainless steel, which can meet most water treatment and transportation conditions. Take 304 stainless steel as an example. The important elements are Ni and Cr. Its nickel (Ni) content is greater than 8%, and its chromium (Cr) content is greater than 18%. Nickel can improve properties such as plasticity, weldability, and toughness of stainless steel. The stainless steel pipe is determined by the chromium content in the steel (there is enough chromium in the steel to react chemically in the air, forming an oxide film on the surface of the steel, which can effectively prevent the internal corrosion of the water pipe. , so the higher the chromium content, the better the corrosion resistance of stainless steel, which has nothing to do with whether the stainless steel water pipe is magnetic or not).

A lot of research and practice at home and abroad have shown that chromium is an element that can passivate steel and make steel stainless, corrosion-resistant, and industrially valuable. This is the principle of corrosion resistance of stainless steel pipes for water.