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Corrosion resistance

The ability of metal materials to resist the corrosive damage of surrounding media

synonym Corrosion resistance (Marine engineering term) generally refers to corrosion resistance

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Corrosion resistance: the ability of metal materials to resist the corrosive damage of surrounding media is called corrosion resistance. By the composition of the material Chemical properties , organizational form, etc. Adding chromium, nickel, aluminum and titanium that can form protective film into steel; change electrode potential The corrosion resistance can be improved by improving the intergranular corrosion of copper, titanium, niobium, etc.

Chinese name: Corrosion resistance
Foreign name: corrosion-proof

Definition: Ability of metal materials to resist damage of surrounding media
determinant: Composition, chemical properties and microstructure of materials
Change electrode potential: Can improve resistance corrosive

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Corrosion resistant alloy

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Objective To study the corrosion resistance of zinc nickel alloy coating. Method passed Orthogonal test method The zinc nickel alloy electroplating process was optimized to obtain the bath formula. adopt Neutral salt spray test The corrosion resistance of the optimized zinc nickel alloy coating was evaluated and compared with that of zinc coating and cadmium coating. The effects of main salt, complexing agent, pH value, current density and temperature on the corrosion resistance of the coating were analyzed. Results The optimal formula was: zinc oxide 6~14 g/L, nickel sulfate 20~30 g/L, sodium hydroxide 100~140 g/L, brightener 4~6 g/L, complexing agent 50~70 g/L. The white rust time of the zinc nickel alloy coating obtained by this formula can reach more than 720 h in neutral salt spray test. Conclusion The corrosion resistance of Zn Ni alloy coating is better than that of zinc coating and cadmium coating.^[1]

Chemical corrosion

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Chemical corrosion is the result of direct chemical interaction between metal and surrounding media. It includes gas corrosion and metal corrosion Non electrolyte There are two forms of corrosion in. Its characteristics are: no current is generated during corrosion; and corrosion products Deposited on the metal surface.^[1]

electrochemistry

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Metal and acid, alkali, salt, etc electrolyte solution Corrosion caused by the action of contact is called electrochemical corrosion 。 It is characterized by current generation during corrosion, and its corrosion products (rust) are not covered on the metal surface as anode, but at a certain distance from the anode metal^[1]

General corrosion

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This kind of corrosion is evenly distributed on the internal and external surfaces of the whole metal, making the cross section continuously reduce, and finally damaging the stressed parts^[1]

Intergranular corrosion

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This kind of corrosion is carried out inside the metal along the grain edge, which usually does not cause any change in the metal shape, and often causes sudden damage to equipment or parts.^[1]

Pitting corrosion

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This kind of corrosion is concentrated in the small area of the metal surface, develops rapidly to the depth, and finally penetrates the metal, which is a more harmful corrosion damage^[1]

Stress corrosion

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It refers to the destruction of metal in corrosive medium under the action of static stress (internal and external stress of metal). This kind of corrosion generally passes through grains, which is called transgranular corrosion^[1]

corrosion fatigue

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It refers to the destruction of metal in corrosive medium under the action of alternating stress. It is also a kind of transgranular corrosion^[1]

corrosion rate

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The weight loss of metallic materials per unit area after corrosion in unit time is called corrosion rate^[1]

Corrosion rate

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The depth of metal material corroded in unit time is called corrosion rate^[1]

Corrosion resistance

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Common use of steel, especially sheet metal surface treatment : When chromium is added, the surface will be very bright. Hexavalent chromium is not allowed. It is generally used as the coating of exposed metal parts. It is beautiful to add nickel to prevent corrosion. It is used with chromium. Generally, zinc is added as a percentage, including Fe//Zn8 zinc coating and Fe//ZnFe (2) 8 zinc iron coating. After plating, thick passivation Disp can be selected. Hexavalent chromium is not allowed Electrophoretic paint , E-Coat, which is relatively cheap and has good corrosion resistance, is easy to fall off in pieces after abrasion. Blackening, soaking in black liquor, this method is the simplest, the cheapest, the worst anti-corrosion effect, Dacromet, expensive, complex process, very good anti-corrosion performance, Delta seal (+Delta Tone), expensive, complex process, very good anti-corrosion performance, Dacromet is often used instead in China, if the requirements are reduced, galvanized is often used.^[1]

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