Corrosion of metals have different classification methods, generally there are several.
First, according to the principles of corrosion free
1, the chemical corrosion of metal surfaces and the surrounding medium caused by the chemical action of corrosion called chemical corrosion. It features no corrosion current generated in the chemical reaction process. Metal in dry gaseous medium and corrosion non-conductive liquid medium (such as alcohol, oil) and, all belong to chemical corrosion.
2, corrosion electrochemical corrosion of metal in a conductive liquid medium occurs due to electrochemical action called electrochemical corrosion, corrosion currents in corrosion progresses. Atmospheric corrosion, seawater corrosion, soil corrosion belong to electrochemical corrosion. Such as carbon steel corrosion in the electrolyte, Fe3C and Fe more positive potential more negative potential, they will form a corrosion micro-cell, Fe3C precipitated hydrogen micro cathode, Fe micro anode corrosion become iron ions. As the potential of a combination of two or more different metal battery is formed in contact with the electrolyte solution and is called a large battery, a positive potential than the metal (e.g. copper) as well a cathode, a potential more negative metal (e.g. iron) and corrosion of the anode .
It should be noted that it is sometimes difficult to chemical corrosion and electrochemical corrosion to clearly separate. Such as steam iron generally occur electrochemical corrosion, but at a high temperature Shique into chemical corrosion, and is difficult to clearly distinguish its temperature limits.
Second, by corrosion damage in the form of classification
1, uniform corrosion when the metal corrosion, the corrosive effect of evenly distributed over the entire metal surface. Such losses caused by corrosion, relatively speaking, it does not harm serious localized corrosion.
2, localized corrosion occurs when the metal corrosion, corrosion effect is concentrated in a certain area, while the rest of the metal is almost no corrosion occurs, the harm caused by this type of corrosion even serious corrosion. Localized corrosion can be divided into: galvanic corrosion, crevice corrosion, pitting, intergranular corrosion, different types of selective corrosion, wear, corrosion and corrosion fatigue.
Various forms of corrosion damage.
Third, in accordance with the specific corrosive environment classification
1, the atmospheric corrosion of metal corrosion in the atmosphere, and any moist gas, which is the most common corrosion.
2, the electrolyte solution corrosion of natural water and most aqueous corrosion of metals, such as acid, alkali, salt aqueous corrosion of metals.
3, ships and marine facilities seawater corrosion occurring in seawater corrosion.
4, buried in the ground soil erosion corrosion of metal structures, such as underground metal pipe corrosion and underground cables.
5, occurs when molten salt corrosion of metal in contact with the molten salt corrosion, such as heat molten salt corrosion of metals.
6, organic atmosphere corrosion of metal in some plastics, rubber and other non-metallic materials volatile organic atmosphere corrosion, such as zinc and cadmium plating layer in an organic acid corrosion atmosphere.
7, certain bacteria biological corrosion, marine biology and human corrosion of metals.
8, corrosion of metal corrosion and other special environment at high temperature water, space and other environment.