Steel, Structural--Testing

Electrochemical conditions within corrosion fatigue cracks
are thought to exert an important influence upon
propagation rate. For the case of cathodically polarized
steel in sea water, it has been observed that pH of
electrolyte adjacent to steel increased and calcareous
material formed on the steel surface. As a consequence of
the latter process the electrochemistry within
cathodically polarized cracks may be unique compared to
other electrolytes. The objective of this study has been
to measure the potential and pH within simulated fatigue
cracks of ABS DH 32 steel under cathodic protection. In
addition, the calcareous deposits which formed within the
simulated cracks were observed and analyzed. Based upon
these data, potential, pH profiles and calcareous deposit
thickness and composition were measured. This, in turn,
permitted conditions within the simulated crack to be
better understood.

The object of this work was to investigate the fatigue
performance of 25.4mm thick, butt welded ABS DH-32 steel
plate under spectrum loading, which simulated the
environmental conditions of the North Sea. Specimens were
tested in sea water under different levels of cathodic
protection. The results, including the previous freely
corroding data, are discussed with regard to the effect of
cyclic - frequency, loading history, weld profile and
cathodic protection. This study indicated that load
interaction effects are negligible in the present
experiments. However, frequency, weld geometry and
cathodic protection significantly effect fatigue life.