8. Prevention by Design

8.3 Causes of Failure in the Context of Design

A good engineering design should provide a maintenance-free service, satisfy the end user, and provide a maximum return on capital in a shortest return period. However, there are several areas related to failure as show below.

Breakdown of protective system

Many protective surface treatments, such as coating and welding, may not be very effective because of the presence of surface irregularities, voids, surface porosity, undercuts, and general surface roughness. The surface heterogeneities act as moisture traps and cause the damage.


Poor fabrication

Factors, such as improper welding, excessive cold working, and excess machining lead to failure.


Lack of accessibility

In complex systems, machinery, and components, there might be inaccessible areas due to lack of design insight where it may not be possible to carry out the corrosion protection measures. Interior of car doors are examples which are subjected to intensive localized corrosion. Figure shows a design which provides adequate air circulation and spraying accessibility.

Structural heterogeneity in materials

Joining similar materials with structural differences, such as differences in thermo-mechanical processing, grain size, number of impurity elements, grain boundary segregates, may cause deviation from the performance expected.


Operating conditions

Factors, such as temperature, pressure, and velocity, influence the service life if allowed to exceed the prescribed limits.