Air, Soil, and Sea Galvanic Corrosion Investigation at Panama Canal Zone

Abstract

Various combinations of metals are used widely in military and industrial equipment. Many of these are deployed worldwide and in many situations under aggressive natural environmental conditions. The object of this study and this paper relates to the effects of subtropical environment on coupled, dissimilar structural metals of military interest. These include aluminum, brass, magnesium, Monel, steel, stainless steel, and titanium alloys. The environments are the atmosphere at Fort Sherman, soil (burial) at Fort Sherman, and seawater (total immersion) at Coco Solo, Panama Canal Zone. Results of this study should have significance in the selection of materials for design of equipment for use in these environments. The atmospheric specimens are rectangular, directly coupled, and offsetted. Offsetting was employed since this would lead to variability in galvanic effects over the exposed surfaces and edges. End grain attack, particularly at the edges of the tempered and aged light alloys, is of interest. For soil burial and seawater immersion, cylindrical specimens connected through a polyacrylate resin cylinder were used. These were selected as suitable and convenient for this purpose. The atmospheric specimens were placed at site in April 1973, and the soil and seawater specimens were located during Oct. 1973. Atmospheric tests are expected to continue for a total period of four years and soil, five years; seawater tests are likely to continue for a total of three and one half years. Atmospheric, soil, and seawater specimens are returned to the laboratory periodically during the test for examination and weight loss determination to assess the effects of each of the environments on the various galvanic couple combinations. Only limited results are available at this early stage of the investigation. Accordingly, no final determination can be made at this time of the significance of results.