I'm painting an iron structure to save it from corrosion and make it look nice. I was advised to apply a layer of primer which I did, it contains iron oxide and is supposed to prevent oxidation. Now I find that the primer itself is not very good in holding on to the iron. It can be easily scraped off with a light use of emery paper. If the layer beneath the paint is this weak how can I expect the paint to hold on and stay put on the metal. Could anyone experienced in this area please advise me. When painting how does the layer of primer feel after application and how does the paint applied with the primer work. Thanks a million.