CORROSION |
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Stress Corrosion Corrosion Fatique Fretting Corrosion Heat Treatment |
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Stress Corrosion |
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Fracture of metal parts attributed to the combinet effects of static applied loads or residual stresses within the metal plus corrosive attack are grouped under the term " stress - corrosion cracking". Just what constitutes a case of this type may difficult in determining but the following indications appear with reasonable consistency. | ||
| The damage is coused by the combined action of sustained stress and corrosive environment applied at the same time. The actual event occurs in two stagees : the period of crack initiation, and the period of crack propagation. Generally, crack initiation results from a physical breakdown of protective surface films and the subsequent corrosive attack on the part. Crack propagation often invloves an electro-chemical attack on the surfaces of the crack, particularly at the crack's apex, in conjuction with the application of stress forces. The rate of corrosive attack on the sides and outer surfaces of the crack is low in comparison to the rate of attack at the apex of the advencing crack. The cracks may be either intergranular ( between the grains ) or transgranular ( across the grains ), but they will be predominantly one way or the other on the particular part. A considerable number of factors determine the direction of crack propagation, such as the alloy type, changes in the composition of the alloy or its environment, the type of heat treatment, the method of metal forming, ad infinitum. Finally, for each type alloy, specific environmental conditions must be present before stress-corrosion can occur. | |||
| Corrosion of fereous metals. | |||
| One of the most familiar types of corrosion is ferrous oxide,.. | |||
| Corrosion of aluminum and aluminum alloys. | |||
| Corrosion attack on aluminum surfaces is usually quite obvious,. | |||
| Corrosion of magnesium alloys. | |||
| Magnesium is the most chemically active of the metals used,. | |||
| Treatment of titanium and titanium alloys. | |||
| Attack on titanium surfaces is generally difficult to detect | |||
| Protection of dissimilar metal contacts. | |||
| Certain metals are subject to corrosion when placed in contact with other metals | |||
| Processes and materials used in corrosion control | |||
| Aircraft parts are almost always given some type surface finish | |||
| Chemical treatment. | |||
| Parco Lubrizing in a chemical treatment for iron and steel parts | |||
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