Corrosive detection assembly for use in a fuel dispensing system to identify presence of a corrosive substance in fuel. The corrosive detection assembly has at least one thermoelectric detector positioned to be in contact with fuel vapor in the fuel dispensing system, the thermoelectric detector producing a detector signal indicating presence of the corrosive substance. The thermoelectric detector includes a sensing circuit having a pair of junctions formed by interconnection of dissimilar conductors, the pair of junctions being configured to experience a substantially equivalent ambient temperature. Electronics are in electrical communication with the thermoelectric detector, the electronics being operative to interpret the detector signal and produce an output if the corrosive substance is present.