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CORROSION AND SURFACE CHEMISTRY OF METALS by Dieter Landolt

CORROSION AND SURFACE CHEMISTRY OF METALS Dieter Landolt ebook
Publisher:
Page: 615
ISBN: 0849382335, 9780849382338
Format: pdf

This behavior also means, however, that high corrosion resistance can be expected only under neutral or oxidizing conditions. The chemical reaction is accompanied by the passage of electrical current. This naturally occurring oxide layer prevents chemical attack of the underlying metal surface. The first is the formation of corrosion cells on a metal surface. Several environmental factors affect the corrosion rates and the composition of the corrosion products, such as metal type, chemical composition of the bulk water, electrochemistry, and microorganisms (Borenstein 1994). Whereas normal condenser water corrosion rates may range between 1 to 5 mils per year (MPY), MIC attack often results in accelerated corrosion rates exceeding 20 MPY and more – causing penetration of some metal surfaces in as little as one or two years. This is a form of corrosion known as pitting. The chemical characteristics of atmospheric moisture nd irrigation moisture affect the rate of corrosion. At the root of these is the inherent instability, at the atomic level, of most industrial metals primarily by two processes. The process of corrosion starts whenever a metal surface is exposed. Minute surface cracks from cells with loss of metal ions from the base of the crack. MOST PIPING IS Installing sufficient shut-off valves to isolate critically weakened areas is well recommended in the event a chemical cleanout produces further leaks – an always present danger. It is an electrochemical process. The term “corrosion” describes a number of processes driven by a wide range of electro-chemical factors. Colonies of micro-organisms generate sticky biofilms which adhere them to their host surface and create a micro-environment that is significantly different from the surrounding metal.