A cargo tank is regularly used to transport lading that is corrosive to the tank itself. Under 49 CFR 180.407, what internal visual inspection interval applies?

49 CFR 180.407(c)

Corrosive lading attacks a tank from the inside, so DOT requires more frequent internal inspection for tanks in that service regardless of how sound the tank looks externally. This is a key safety distinction a driver or inspector must apply correctly.