The deterioration of metals caused by the environment and medium is very common. The destruction of most metal articles is related to corrosion factors except for a few precious metals such as Au and Pt. Metal corrosion causes huge losses to society, therefore, anti-corrosion has become a critical issue that must pay attention to.
Corrosion is one of the major causes of damage to metal products, specialized anti-corrosion solutions should be applied to prolong the life cycle of metal products according to the feature that metal products are easily corroded. Chemical, physical, and electrochemical protection are the most common methods.
Corrosion can be categorized into five types, general corrosion, pitting, intergranular corrosion, selective corrosion, and stress corrosion cracking. General corrosion affects the entire surface of a metal, commonly known as rust. Pitting occurs in the small holes on the surface of the material, and these holes become larger over time. Intergranular corrosion is almost invisible on the surface as it takes place inside. Selective corrosion erodes only components of complex materials. This type of corrosion starts from the surface and then penetrates to the interior and corrodes at different speeds. Stress corrosion cracking happens when the material bears the ultimate tensile strength.
Four Common Anti-Corrosion Methods:
Some heavy metals are low chemical active and not easily corroded, so the service life of the compound metal is extended with a great margin when adding heavy metals to other metals. People mix nickel, chromium, etc. with steel to make stainless steel, for instance.
There are two types of protective layers metal and non-metal. Common non-metal layers include oil paint, ceramic, and plastic coatings. Electroplating and hot plating generally use non-corrosive metals, such as zinc, tin, chromium, or nickel to form an oxide film on the surface.
Electrochemical protection is a method based on the galvanic cell theory by eliminating the galvanic cell reaction which is the cause of chemical corrosion. The cathodic method is more widely used than the anodic method.
Corrosive Medium Treatment
This method is achieved by eliminating corrosive medium. In other words, keeping the metal machinery dry, to name a couple, wiping off the moisture on the equipment, or adding a corrosion inhibitor to corrosive medium.