We used the POR-15 on the areas of fthe floor, and underside where there was rust present- we stripped down and wired wheeled all the rust we could from the metal - then cleaned and etched the metal with POR-15's marine clean and prep & ready before we painted the POR-15 on- then we shot over the POR-15 with Epoxy primer (or if the section wasn't being finish painted- we applied a coat of Chassis coat black over the POR-15). We have yet to see any adverse reactions betweent he POR-15 and the epoxy but keep in mind we only used the POR-15 on areas that had rust that we wanted to encapsulate places with solid metal that we weren't going to replace with new steel. The POR-15 is not supposed to be used as a finshed paint product-