Corrosion phenomena influencing factors

It is important to know where titanium might exhibit susceptibility to corrosion attack in order to establish which corrosion test methods may be applicable or relevant to titanium alloys. Table 2 presents a list of specific environments where some form of corrosion susceptibility has been observed on titanium alloys in laboratory tests or service experience. The table indicates the relevant mode of corrosion degradation that can be expected, general scope of titanium alloys susceptible, and comments on critical factors that strongly influence each corrosion phenomenon. 

These tests are conducted in closed cabinets with controlled atmospheres, so that it is possible to change the factors that influence the corrosion phenomenon, with a view to ensuring an increase in its kinetics, without there being any change in the corrosion mechanism. Although these experiments are generally designed to produce similar results to those obtained in natural conditions, they do not always fully coincide. However, accelerated experiments are normally used in the comparative evaluation of materials and in their quality controls. 

Impediments to water flow resulting from inadequate equipment design or lodgement of foreign objects in the tubes can exercise a dramatic effect on the erosion-corrosion process. Much of this influence is linked to the creation of turbulence and the simple increase in fluid velocity past obstructions. The importance of these factors is quickly recognized when the phenomenon of threshold velocity is considered. 

It will be necessary to establish some correlations between the reciprocal influences of various degrada-tive factors in order to better understand the aging phenomenon. Intensive studies must be undertaken in polluted atmospheres in order to establish the action of corrosive and pollutant agents whose concentration in the environment increases continuously. 

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