The development of a quantitative method for evaluating the resistance of aluminum to pitting corrosion in sea water is described. The method is based on a statistical treatment of penetrometer measurements of every pit present on test specimens immersed in sea water for periods up to 24 months. Normal frequency distributions were obtained by plotting the frequency of pitting against the square root of the pit depth. Calculations of the mean square root pit depth, the standard deviation, and standard error of the mean square root pit depth are shown. The importance of the mean square root pit depth, the standard deviation, and the frequency of pitting in determining the manner by which pitting corrosion proceeds is discussed.

A sampling procedure method is described wherein quantitative data on the resistance of aluminum to pitting corrosion in sea water can be obtained within useful limits of confidence by statistical analysis of measurements of only a fraction of the total number of pits present.