Page 384 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

362 CONSEQUENCES OF CORROSION

Figure 5.48 Dark red and greenish spots on the outside surface (19).

corner of the keyway (Sastri et al. (19), p. 500, Fig. 7.51). Transverse cross sections
had secondary cracks (Sastri et al. (19), p. 500, Fig. 7.52). The conveyor drive shaft
failed because of corrosion fatigue in bending. The failure was initiated at both cor-
ners of the keyway. Many cracks were observed, indicating the presence of a large
number of stress concentrator sites resulting from pitting. Fatigue cracks initiate at
sites of maximum stress and minimum local strength.
The failure of the conveyor drive shaft can be prevented by the use of protective
coatings or other means of shielding the shaft from a corrosive medium.

Failure of Copper Pipe in a Sprinkler System Straight sections and T-sections
were examined along with the analysis of water for corrosion products for micro-
biological activity. The straight sections of the pipe showed dark red and greenish
spots on the surface (Fig. 5.48); through-wall pits were present in the red spots. The
T-sections did not have red spots (Fig. 5.49), but one sample had a crack (Fig. 5.50).

Figure 5.49 The exterior surface without red spots (19).