A water based, rust converting, chelating-polymer primer which reacts with ‘rust’ to produce a stabilised layer for painting. It reacts quickly with the rust and transforms the typical orange/brown iron oxides (rust) into a more stable and insoluble blue/black complex. This blue/black layer is ready for painting when dry and reacted. It is not necessary to wash the surface with water before painting. It is an excellent adhesion promoter for subsequent coating systems.