CORROSION

Stress Corrosion Corrosion Fatigue Fretting Corrosion Heat Treatment

Forms of Corrosion

These many forms of corrosion. The form of corrosion depends on the metal involved, its size and shape, its specific fuction, atmosperic condition, and the corrosion - producing agents present. Those described in this section are the more common forms found on airfame structures.

Forms of Corrosion

Type of Corrosion

Corrosion Control

Corrosion Removal

Preventive Maint.

Surface Corrosion. Surface corrosion appears as a general roughening,etching,or fitting of the surface of a metal, frequently accompanied by a powdery deposit of corrosion product. Surface corrosion may be caused by either direct chemical or electrochemical attack. Sometimes corrosion will spread under the surface coating and cannot be recognized by either the roughening of the surface or the fowdery deposit, Instead, the paint or plating will be lifted of the surface in small blisters which result from the pressure of the underlying accumulation of corrosion products. Disimilar Metal Corrosion. Extensive pitting damage may result from contect between disimilar metal parts in the presence of a conductor. While surface corrosion may or may not be taking place, a galvanic action, not unlike electroplating, occurs at the points or areas of contact where the insulation has broken down or been ommited. This electrochemical attack can be very seriouse because the action is, in many instances, taking place out of sight, and the only way to detect in prior to structural failure is by disassembly an inspection. Intergranular Corrosion. This type of corrosion is an attack along the grain boundaries of an alloy and commonly results from a lack of uniformity in the alloy structure. Alluminum alloys and some stainless steel are particularly susceptible to this form of electrochemical attack. The lack of uniformity is caused by changes that occur in the alloy during heating and cooling. Intergranular corrosion may exist without visible surface evidence. Very severe intergranular corrosion may sometimes cause the surface of a metal to " exfoliate." This is a lifting or flaking of the metal at the surface due to delamination of the grain boundaries caused the pressure of corrosion residual product built up. This type of corrosion is difficult to detect in its original stage. Ultrasonic and addy current inspection methods are being used with a great deal of success.

Common Corrosive

List of Agent

Bugs