Answer
As discussed in Section 17.7 of this book,
1. Galvanic Corrosion- occurs when two metals or alloys having different compositions are
electrically coupled while exposed to an electrolyte.
2. Crevice corrosion – type of electrochemical corrosion that occurs as a consequence of concentration difference of ions or dissolved gases in electrolyte solution or in between two regions of same metal. Usually in crevices where the solution becomes stagnant.
3. Pitting- a very localized corrosion attack in which small pits or holes form. It penetrates from the top of horizontal surface downward in a nearly vertical direction. Same mechanism with crevice corrosion.
4. Intergranular corrosion- occurs along grain boundaries for some alloys that results to the disintegration of macroscopic specimen along its grain boundaries. Alloys if heated to temperatures between 500 deg Celsius to 800 deg Celsius will become senitized to intergranular attack.
5. Selective leaching- usually found in solid solution and occurs when one element is preferentially removed as a consequence of corrosion processes.
6. Erosion corrosion- arises from the combined action of chemical attack and mechanical abrasion or wear as a consequence of fluid motion. Relatively soft metals such as copper and lead are also sensitive to this form of attack. Usually it can be identified by surface grooves and waves having contours that are characteristic of the flow of the fluid.
7. Stress corrosion- results from the combined action of an applied tensile stress and a corrosive environment; both influences are necessary. The stress that produces stress corrosion cracking need not be externally applied; it may be a residual one that results from rapid temperature changes and uneven contraction or occur for two-phase alloys in which each phase has a different coefficient of expansion.
8. Hydrogen embrittlement- occurs when there is a significant reduction in ductility and tensile strength when atomic hydrogen penetrates the material. A number of mechanisms have been proposed to explain hydrogen embrittlement and most are based on the interference of dislocation motion by the dissolved hydrogen.
Work Step by Step
As discussed in Section 17.7 of this book,
1. Galvanic Corrosion- occurs when two metals or alloys having different compositions are
electrically coupled while exposed to an electrolyte.
2. Crevice corrosion – type of electrochemical corrosion that occurs as a consequence of concentration difference of ions or dissolved gases in electrolyte solution or in between two regions of same metal. Usually in crevices where the solution becomes stagnant.
3. Pitting- a very localized corrosion attack in which small pits or holes form. It penetrates from the top of horizontal surface downward in a nearly vertical direction. Same mechanism with crevice corrosion.
4. Intergranular corrosion- occurs along grain boundaries for some alloys that results to the disintegration of macroscopic specimen along its grain boundaries. Alloys if heated to temperatures between 500 deg Celsius to 800 deg Celsius will become senitized to intergranular attack.
5. Selective leaching- usually found in solid solution and occurs when one element is preferentially removed as a consequence of corrosion processes.
6. Erosion corrosion- arises from the combined action of chemical attack and mechanical abrasion or wear as a consequence of fluid motion. Relatively soft metals such as copper and lead are also sensitive to this form of attack. Usually it can be identified by surface grooves and waves having contours that are characteristic of the flow of the fluid.
7. Stress corrosion- results from the combined action of an applied tensile stress and a corrosive environment; both influences are necessary. The stress that produces stress corrosion cracking need not be externally applied; it may be a residual one that results from rapid temperature changes and uneven contraction or occur for two-phase alloys in which each phase has a different coefficient of expansion.
8. Hydrogen embrittlement- occurs when there is a significant reduction in ductility and tensile strength when atomic hydrogen penetrates the material. A number of mechanisms have been proposed to explain hydrogen embrittlement and most are based on the interference of dislocation motion by the dissolved hydrogen.
