Corrosion and Its Control Measures
CORROSION AND ITS CONTROL
CORROSION * corrosion can be defined as the degradation of a material due to a reaction with its environment. * Degradation implies deterioration of physical properties of the material. This can be a weakening of the material due to a loss of cross-sectional area, it can be the shattering of a metal due to hydrogen embrittlement, or it can be the cracking of a polymer due to sunlight exposure. * Materials can be metals, polymers (plastics, rubbers, etc.), ceramics (concrete, brick, etc.) or composites-mechanical mixtures of two or more materials with different properties. Because metals are the most used type of structural materials most of this web site will be devoted to the corrosion of metals. * Most corrosion of metals is electrochemical in nature.
TYPES OF CORROSION * UNIFORM CORROSION * GALVANIC CORROSION * CONCENTRARION CELL CORROSION * PITTING CORROSION * CREVICE CORROSION * FILLI FORM CORROSION * INTERGRANULAR CORROSION * STRESS CORROSION CRACKIN * CORROSION FATIGUE * FRETTING CORROSION * EROSSION CORROSION
Uniform Corrosion * This is also called general corrosion. The surface effect produced by most direct chemical attacks (e.g., as by an acid) is a uniform etching of the metal. On a polished surface, this type of corrosion is first seen as a general dulling of the surface and, if allowed to continue, the surface becomes rough and possibly frosted in appearance. The discoloration or general dulling of metal created by its exposure to elevated temperatures is not to be considered as uniform etch corrosion. The use of chemical-resistant protective coatings or more resistant materials will control these problems. * While this is the most common form of corrosion, it is generally of little engineering significance, because structures will normally become unsightly and attract maintenance long before they become structurally affected. The facilities shown in
CORROSION * corrosion can be defined as the degradation of a material due to a reaction with its environment. * Degradation implies deterioration of physical properties of the material. This can be a weakening of the material due to a loss of cross-sectional area, it can be the shattering of a metal due to hydrogen embrittlement, or it can be the cracking of a polymer due to sunlight exposure. * Materials can be metals, polymers (plastics, rubbers, etc.), ceramics (concrete, brick, etc.) or composites-mechanical mixtures of two or more materials with different properties. Because metals are the most used type of structural materials most of this web site will be devoted to the corrosion of metals. * Most corrosion of metals is electrochemical in nature.
TYPES OF CORROSION * UNIFORM CORROSION * GALVANIC CORROSION * CONCENTRARION CELL CORROSION * PITTING CORROSION * CREVICE CORROSION * FILLI FORM CORROSION * INTERGRANULAR CORROSION * STRESS CORROSION CRACKIN * CORROSION FATIGUE * FRETTING CORROSION * EROSSION CORROSION
Uniform Corrosion * This is also called general corrosion. The surface effect produced by most direct chemical attacks (e.g., as by an acid) is a uniform etching of the metal. On a polished surface, this type of corrosion is first seen as a general dulling of the surface and, if allowed to continue, the surface becomes rough and possibly frosted in appearance. The discoloration or general dulling of metal created by its exposure to elevated temperatures is not to be considered as uniform etch corrosion. The use of chemical-resistant protective coatings or more resistant materials will control these problems. * While this is the most common form of corrosion, it is generally of little engineering significance, because structures will normally become unsightly and attract maintenance long before they become structurally affected. The facilities shown in