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INTRODUCTION
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CORROSION PREVENTION MANUAL VOLUMES 1 AND 2 INTRODUCTION
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Volume 1
INTRODUCTION
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Volume 1
INTRODUCTION
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1. General
A. The ability to recognize corrosion in its early stages is required to enable
corrective action to be taken before costly repairs or replacements become
necessary.
2. Identification
A. Aluminum Alloys --Corrosion of the aluminum surface is usually indicated by
whitish powdery deposits with dulling of the surface on unpainted parts. The
white powdery deposit also forms at discontinuities in protective coating
and may spread beneath paint causing blistering or flaking. As the corrosion
attack advances, the surface will appear mottled or etched with pitting.
Swelling or bulging of skins or pulled or popped rivets are often visual
indications of corrosions.
B. Alloy and Carbon Steels -- Corrosion is indicated by red rust deposits and
pitting of the affected surfaces.
C. Corrosion Resistant Steels -- Corrosion is indicated by black pits or a uni-form reddish-brown surface.
3. Types
A. The terminology used in describing corrosion is based on either the appear-ance of the corrosive attack or the mechanism associated with its formation.
Frequently, several types of corrosion will occur simultaneously and it
becomes difficult to determine the specific cause.
B. The following types of corrosion are those most commonly experienced:
(1)Surface Corrosion --Visible as uniform etching of the metal surface,
and results from direct chemical attack.
(2)Pitting --Detected as a series of pits on the metal surface, usually in
small, well-defined local areas (Fig. 1).
(3)Exfoliation -- Inter granular corrosion characterized by bulging or
blistering of the metal surface, resulting from the force created by
expanding corrosion products at the grain boundaries (Fig. 2).
(4)Galvanic --Usually visible as pitting and is often referred to as dis-similar metal corrosion. However, it is not limited to just dissimilar 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：757 防腐手册 CORROSION PREVENTION MANUAL 第二册 一般信息(8)
