Chapter 8: Corrosion and Degradation of Materials

there is actual material loss either by dissolution (corrosion) or by the formation of nonmetallic scale or film (oxidation).

are relatively resistant to deterioration, which usually occurs at elevated temperatures or in rather extreme environments

For polymers, mechanisms and consequences differ from those for metals and ceramics, and the term ___ is most frequently used

Polymers may dissolve when exposed to a liquid solvent, or they may absorb the solvent and swell; also, ___ (primarily ultraviolet) and heat may cause alterations in their molecular structures

*___ of an object occurs as a result of the interaction between the environment or with the materials that form the object *several ways in which ceramics break down physically and chemically

it is in the nature of all the materials used for construction to eventually ___ and ___

the destructive electrochemical attack of a material

why metals corrodes?

two reactions necessary in corrosion of zinc in acid

occurs when the iron in the metal oxidises

solution for steel rusting

generated by coupling to the standard hydrogen electrode, standard half-cells for various metals and ranking them according to measured voltage

the rate of material removal as a consequence of the chemical action, is an important corrosion parameter

The variables in the corrosion environment, which include ___ can have a decided influence on the corrosion properties of the materials that are in contact with it.

In most instances, increasing fluid velocity enhances the rate of corrosion due to

Increasing the concentration of the corrosive species (e.g., H+ ions in acids) in many situations produces a more rapid rate of

forms of corrosion

work together at crack tips

break down of passivating layer by erosion (pipe elbows)

downward propagation of small pits & holes

between two pieces of the same metal

Dissimilar metals are physically joined. The more anodic one corrodes

corrosion along grain boundaries, often where special phases exist

preferred corrosion of one element/constituent