Chipping or chip, Corrosion, Surface Corrosion, Dissimilar metal corrosion, Stress corrosion, Fretting corrosion

Tabel 2.1 f

DEFFECT	DESCRIPTION
Chipping or chip	Breaking out of small pieces of metal which have been removed mechanically. Usual cause is a concentration of stress due to nick, scratches, inclusions, peening, or careless handling of parts. Do not confuse with flaking.
Corrosion	Metal corrosion is the deterioration of the metal by chemical or electrochemical attack, water of water vapor containing salt combined with oxygen in the atmosphere produce the main source of corrosion in engines. Engines operating near the sea or in areas where the atmosphere contains industrial fumes which are corrosive are susceptible to corrosion attack. Corrosion may change the smooth surface, weaken the interior or damage and lossen adjacent parts. In some cases treatment of parts especially ligh alloys take place by corrosion caused by fabrication. An electrochemical attach may be linked chemically to the electrolytic reaction which takes place in electroplating, anodizing, etc
Surface Corrosion	Appears as a general roughness, or pitting of the surface of the metal. Sometimes corrosion will spread under the surface coating and cannot be recognized either by roughening of the surface or the powder deposit (rust). In case like this, the paint or plating will be lifted off in surface in small blisters which results from the pressure of the underlying accumulation of corrosion products.
Dissimilar metal corrosion	Excessive pitting damage may result from contact between dissimilar metal parts in presence of a conductor. While suface corrosion may or may not take place, a galvanic action not unlike electroplating occurs at the point of areas of contact where the insulation has broken down or being omitted. This electrochemical attach can be serious because the action is, in many instances, taking place out of sight and the only way to detect it is by disassembly and inspection.
Stress corrosion	Stress corrosion occurs as a result of the combined effect of sustained tensile stresses and corrosive environment. Stress corrosion cracking is found in most metal systems especially of aluminum, copper, certain stainless steels and high srtength alloy steels. Aluminum alloy parts with pressed in bushings, clevis, pin, joints, shrink fits and overstressed nut are examples of parts which are suscestible to stress corrosion cracks.
Fretting corrosion	Is a form of corrosion attach which occurs when two matting surfaces, normally at rest with respect to one another are subject to a slightly relative motion. It is characterized by pitting on the surfaces and the generation of considerable quantities of finely devited debris. Since the restricted movements of the two surfaces prevent the debris from escaping, an localized abrasion is occurs. The presence of water vapor increases this type of deterioration.