The interior of a structurally sound tank may be lined with a thick layer of noncorrodible material. The lining material and application method must comply with applicable industry codes. The lining used must also meet the same federal requirements as for repaired tanks (40 CFR 280.33). Note: Flexible inner liners (bladders) that fit inside a tank do not meet the tank interior lining requirements. Tanks using only an interior lining for corrosion protection must pass an internal inspection within 10 years and every 5 years after that to make sure that the tank and lining are sound. You should keep records of these inspection results.
Photographs of tank lining can be found at www.epa.gov/oust/graphics/tlpics.htm