Pitting Corrosion

Pitting is the most common corrosive attack on aluminum alloy products. Pits form at localized discontinuities in the oxide film on aluminum exposed to atmosphere, fresh water, or saltwater, or other neutral electrolytes. Since in highly acidic or alkaline solutions the oxide film is usually unstable, pitting generally occurs in a pH range of about 4.5–9.0.

The  pits can be minute and concentrated and can vary in size and be widely scattered, depending on alloy composition, oxide film quality, and the nature of the corrodent. The resistance of aluminum to pitting depends significantly on its purity; the purest metal is the most resistant.

The presence of other elements in aluminum, except Mn, Mg, and Zn, increases in susceptibility to pitting. Copper and iron have the greatest effect on susceptibility. Alclad alloys have greatest resistance to penetration since any pitting is confined to the more anodic cladding until the cladding is consumed.

READ MORE.......

J. G. Kaufman
Kaufman Associates
Columbus, Ohio

Mechanical Engineers’ Handbook: Materials and Mechanical Design, Volume 1, Third Edition.
Edited by Myer Kutz
Copyright  2006 by John Wiley & Sons, Inc.



for more details and updates about autocad simple tutorial please visit.........
www.autocadsimpletutorial.blogspot.com

Berbagi :