Why your valves would corrode?

Corrosion is the destruction and deterioration of materials under the influence of various environments. Corrosion is one of the important factors that cause valve damage. Therefore, in the use of valves, corrosion protection is the first consideration. Let us look at the relevant knowledge of valve corrosion.

The form of metal valve corrosion

There are two forms of metal valve corrosion: uniform corrosion and local corrosion. The rate of uniform corrosion can be evaluated by the annual average corrosion rate. Metal materials, graphite, glass, ceramics and concrete, divided into 4 grades according to the size of the corrosion rate; The corrosion rate is less than 0.05mm / a is excellent; the corrosion rate is 0.05 ~ 0.5mm / a is good; the corrosion rate is 0.5 ~ 1.5mm / a can be used; the corrosion rate is greater than 1.5mm / a is not applicable, Valve sealing surfaces, stems, diaphragms, small springs and other valve parts are generally made of first-grade materials, and second- or third-grade materials are suitable for valve bodies and bonnets.

Uniform corrosion is performed on the entire surface of the metal. Such as stainless steel, aluminum, titanium and other protective film produced in an oxidizing environment, the state of the metal under the film is uniformly corroded. There is also a phenomenon that the metal surface is corroded and peeled off. This kind of corrosion is the most dangerous. Local corrosion occurs at the local position of the metal, and its forms include pitting corrosion, crevice corrosion, intergranular corrosion, delamination corrosion, stress corrosion, fatigue corrosion, selective corrosion, wear corrosion, cavitation corrosion, vibration corrosion, hydrogen eclipse, etc. Different corrosion forms have their own characteristics.

The form of Non-metal corrosion

Non-metallic corrosion is the same as metal corrosion. Most non-metallic materials are non-electrical conductors, and generally do not cause electrochemical corrosion, but purely chemical or physical corrosion. This is the main difference from metal corrosion. Non-metallic corrosion does not necessarily cause weight loss but tends to increase weight. For metal corrosion, weightlessness is the main factor. Non-metallic corrosion is mostly caused by physical action, and metal corrosion is very rare. Internal corrosion of non-metallic metals is a common phenomenon. And metal corrosion is mainly surface corrosion.

After the metal material contacts the medium, the solution or gas will gradually diffuse into the material, causing a series of non-metallic corrosion changes. According to the type and variety of non-metallic materials, the corrosion forms are different. The forms of corrosion include dissolution, swelling, bubbles, softening, decomposition, discoloration, deterioration, aging, hardening, and fracture. However, from a comprehensive point of view, the corrosion resistance of non-metals is much better than that of metal materials. The strength of non-metal materials is lower than that of metal materials.

After understanding the corrosion pattern of the valve, we can take corresponding anti-corrosion measures accordingly. In the next article, we will show you how to carry out valve anticorrosion. Follow us to learn more about valve.