We have a 316L SS mobile tank that we recently found with horizontal lines (relating to product level) of - Heavy "rust" stains about 1/8" wide by a couple of inches to a couple of feet long - deep corrosion 1/8" wide, up to 1/8" deep by a 1/4" to a couple of inches long - heavy "rust" stains bleeding down from the line of corrosions. However, along the same horizontal line, other areas in the tank are fine. The product is sodium chlorate solution loaded at about 175 degrees F. (However that does not exclude something else from accidently being loaded in the tank.) We have other tanks in the same service with no indication of the same problem. There are a total of three different horizontal corrosion / stain lines in the tank. This means the corrosion occurred over 3 different product loads. The appearance of the material in the corrosion pits was jagged. Any ideas what could have caused this corrosion? Thanks