ASTM D1275 Corrosive Sulfur in Electrical Insulating Oils – Silver Corrosion Procedure
Insulating oils (transformer oils) protect transformer coils from electrical and thermal damage. If corrosive sulfur compounds are present in the oil, they may react with system components and compromise performance. This test determines the presence of corrosive sulfur in insulating oils. It has two options: Method A (140°C, 19 hours) and a Method B (150°C, 48 hours). Method B is normally the preferred method.
The sample oil is placed in the test vessel and a freshly polished silver strip is added. Nitrogen is bubbled through the oil, the vessel is covered and heated to the test temperature for the test time. The silver strip is removed, cleaned and examined. Any sulfur compounds present in the sample will react with the silver to form a black substance. Reported is “corrosive” or “non-corrosive”