Statistical analysis on corrosion of oil storage tank bottom plate - Development of corrosion preventive bottom plate for oil storage tanks (part 1)

From extreme value statistical analysis on corrosion rate of bottom plates of oil storage tanks, following results are provided. With heating oil storage tanks installed on sand base and non-heating oil storage tanks installed on asphalt base, corrosion rates of bottom plate are the largest, and the extent of it is reduced in order of non-heating sand base tanks, heating asphalt base tanks. In most non-heating asphalt base tanks, corrosion of bottom plate is restrained, but in some cases, high corrosion rates were almost equal to that in sand base tanks with heating. In such cases, corrosion rate was large and statistics on corrosion rate in sand base tanks and in non-heating asphalt base tanks showed almost the same. It was indicated by direct observation of bottom plates that the presence of airgap between base and bottom plate accelerates corrosion rate. The present counter-measure such as installation of oil storage tanks on asphalt base is not necessarily adequate. The studies on new corrosion prevention method with enough effect which can expect even if gap exists between base and bottom plate, will be the most important subject.