PANELS exposed in aqueous media frequently do not corrode uniformly. Many show signs of local attack, especially on edges or corners. For these panels weight-loss comparisons are meaningless (2) unless made between panels having essentially the same type of corrosion. An opinion as to the reliability of these comparisons may be based on the nature of the localized corrosion. Obviously if localized corrosion is limited to pits of about the same number and depth on two panels, their relative order of corrosion resistance may be based on weight loss—but the primary criterion which places these two panels in the same class is the nature of the corrosion.
For these reasons our laboratory, for the past six years, has used a visual scoring method supplemented by the customary weight-loss data. Scores are obtained by marking various criteria of corrosion on a prepared form (Form 1.) which is converted to a numerical...
