Chassis black is not a rust prohibitor or prevention. Super heap or repco or your local industrial supplies can order 4 or 5l tins of tectyl which is a rust prevention. Your chassis must be cleaned smick as before you do it and after washing it wait for 4 sunny days for it to dry before you spray it. If water is trapped under your rust prohibitor then u have made a massive problem. Endrust now warrant their product for anyone's info.