Fangjing corrosion test report third
Tianjin Rong Da Testing Co., Ltd. contact: Wang Jingfu
Cell phone: 13102238283 QQ:3144667033
Telephone: 022-23892103
Intergranular corrosion is a local corrosion of metal materials occurred along the grain boundaries of the material in corrosive medium, in particular, the corrosion in metal (alloy) without any changes in surface conditions, the grains lose binding force, the strength of the metal is completely lost, resulting in sudden destruction of equipment. Intergranular corrosion is mainly due to the difference of the chemical composition between the surface and the inside of the grain, and the existence of grain boundary impurities or internal stress. The combination of intergranular corrosion and intergranular failure greatly reduces the mechanical strength of the metal. But after the occurrence of surface corrosion of metals and alloys still maintain certain metallic luster, do not see signs of destruction, but the binding force between grains decreased and the deterioration of mechanical properties, can not withstand the strike, so it is a very dangerous corrosion. Usually occurs in brass, aluminium alloy and stainless steel, nickel base alloy.
Corrosion classification:
First, according to the environment: wet etching, dry etching, etching anhydrous organic liquid and gas, corrosion and slag in molten salt;
Two, according to the classification of corrosion mechanisms: chemical corrosion, electrochemical corrosion, physical corrosion.
Three, according to the corrosion morphology: general corrosion, local corrosion (including intergranular corrosion due to grain boundary impurities or because of some alloy elements at grain boundaries increase or decrease the occurrence of corrosion in the grain boundary, and along the grain boundary to the depth of development).
Corrosion cracking under the action of stress: crack and fracture failure under the action of stress and corrosion environment;
Hydrogen damage: the existence of hydrogen in metal materials or the interaction with hydrogen, resulting in deterioration of the mechanical properties of the phenomenon of metal.
Including: 1 hydrogen corrosion (high temperature, high pressure, infiltration of the hydrogen atoms in the steel and the C and Fe3C reaction of methane, resulting in the phenomenon of cracks and bubbles in the material),
2 (the hydrogen atom of hydrogen embrittlement, corrosion, electrolytic pickling or reaction medium containing hydrogen produced by diffusion into the metal of the metal hydride generation or dislocations in the metal material, causing embrittlement phenomenon called 3 hydrogen embrittlement; hydrogen embrittlement of the material under the action of the stress brittle fracture phenomenon called hydrogen embrittlement crack) hydrogen bubble, (caused by steel corrosion of steel into the nascent hydrogen reaction or other process, (especially low strength steel) surface local uplift phenomenon),
4 hydrogen induced cracking (the steel internal along a ladder shaped crack damage was rolled into the direction of the nascent hydrogen generated in the process of steel corrosion,), stress oriented hydrogen induced cracking (under the action of stress, crack of steel ladder generated along with the main stress direction the vertical (wall thickness direction) to an extension, through whole failure form of wall thickness). ,