| serial | name | amount of symbols | unit symbol | meaning | corrosion resistance | corrosion resistance of metallic materials to resist the surrounding medium (air, steam, harmful gases, acids, alkalis, salts, etc.) to the corrosive effects of ability. The corrosion resistance of metals is related to many factors, such as metal chemical composition, processing properties, heat treatment conditions, the organization of the state and the medium and temperature and so on. | chemical corrosion | chemical corrosion of the metal with the surrounding medium are directly the result of chemical reaction. It includes gas corrosion and metal corrosion in non-electrolyte in two forms. Its characteristics are: the corrosion process does not generate electricity; and the corrosion product deposition on the metal surface. | 1 | electrochemical corrosion | / | / | metal in contact with the electrolyte solution of acid, alkali, salt, caused by corrosion, known as electrochemical corrosion. It is characterized by the current generated in the corrosion process, corrosion products (rust) does not cover the surface of the metal as the anode, but a certain distance from the anode metal. | 2 | general corrosion | / | / | this corrosion is evenly distributed throughout the metal inner and outer surfaces, so that the cross section decreasing, and ultimately by the power failure. | 3 | intergranular corrosion | / | / | this corrosion within the metal along the grain edge, usually does not cause any change in the metal shape, tend to make the equipment or parts to sudden destruction. | 4 | pitting corrosion | / | / | this corrosion concentrated in a small metal surface area, and quickly to the depths of the development, and finally penetrate the metal is a hazard than the large corrosion damage. | 5 | stress corrosion | / | / | (both within and outside the metal stress) under the action of static stress, the metal in the corrosive medium caused the damage. This corrosion medium to listen to the damage caused by it is also a transgranular corrosion. | 6 | corrosion fatigue | / | / | refers to the destruction of the alternating stress, caused by the metal in the corrosive medium. It is also a transgranular corrosion. | 7 | corrosion rate | / | mg / (dm2 · d) or g / (dm2 · d) | per unit area of the metal material in the unit time corrosion after weight loss, known as the corrosion rate. | 8 | corrosion rate | R | mm / a | metal material in the unit time is called the corrosion rate. | two | antioxidant activity | / | g / (cm2 · h) Or mm / h | metallic materials at room temperature or high temperature resistance to oxidation. Metal oxidation process is actually a form of belonging to chemical corrosion. It can be used directly after the corrosion of the metal surface by the weight loss within a certain period of time, size, speed metal weight loss. | three | chemical stability | / | / | means of metallic materials resistant to corrosion and oxidation resistance in general. The chemical stability of metal materials at elevated temperatures is called thermal stability. |