Study of corrosion on copper strips by petroleum naphtha in the ASTM D-130 test by means of electronic microscopy (SEM) and energy dispersive X-ray (EDX)

Summary Corrosion in heat-engines has been attributed to some undesirable sulfur compounds present in petroleum naphthas, fuel-oils or gasolines. The corrosivity of these petroleum products is measured by means of the ASTM D-130 copper strip test, which is based on discoloration of a standard copper strip immersed into the petroleum products at 50°C for 3 h. The present paper studies various aspects of corrosivity of different sulfur compounds in petroleum naphthas by means of the ASTM D-130 test together with the electronic microscopy (SEM) and energy dispersive X-ray (EDX) techniques. These non-destructive techniques allow to know the strip corrosive morphology and to determine the sulfur concentration on this strip. Of the various types of sulfur compounds present in petroleum naphthas, the data show that elemental sulfur is corrosive to copper, but its corrosive level differes from naphtha to naphtha. Among the different mercaptans only ethyl-mercaptan presents corrosivity. The disulfides and sulfides tested are non-corrosive to copper.