Abstract
One of the authors (T. M.) has investigated the effect of pH on the corrosion fatigue behaviour of a low carbon steel, and reported the relationship between the corrosion fatigue life and pH. The present work has been carried out to make clear the effect of pH on the fatigue crack propagation rate of the same material, and the results are compared with the previous data. Experiments have been made of fatigue crack propagation of 0.15% carbon steel in aerated HCl-NaCl-NaOH solutions with different pH values of pH 0.5, 5.3 and 11.2, at 25°C. In the acidic solution of pH 0.5, the crack propagation rate was an order of magnitude greater than that in the solution of pH 5.3 or pH 11.2. In the slightly acidic or in alkaline solution (pH 5.3 and pH 11.2), the crack propagation rate was influenced by the stress intensity factor, K. Some wedging effect by solid corrosion products formed on fatigue surface was also observed. At low K values, crack propagation rate was greater in the alkaline solution of pH 11.2 than that in the solution of pH 5.3. Increasing the K value tended to show a reversed relationship in the propagation rate between pH 5.3 and pH 11.2. The pH dependence of crack propagation rate was in good accord with previous results of pH dependence on the fatigue life as a function of cyclic stress amplitude.
