Recoatability: Zero Rust and Rust Shield will recoat with fewer problems because both chemical and mechanical bonding mechanism are still available. The moisture cured Urethanes, POR, Rust Bullet, et al only have mechanical available becuse the chemical bond sites are taken up in the process of catalyzation. The "moisture-cures" use the moisture in the atmosphere to cure the film. This curing process results in a product that will require tie-coats etc to facilitate adhesion........ On the epoxy primer front, To my way of thinking the use of the alyds DTM (direct to metal) precludes the need for the epoxy primers at all. My point to users is to use ZR or ?? to lock down any existing rust, let the ZR go to full cure and then build your sandable system on top of that. Here's something for all of us to think about. If, your project has totally prepared white metal blasted steel, why wouldn't one just go with the automotive "sytem" from the steel up? These rust and corrosion control coatings have a place, but is this it? I would like to hear everyone's ideas on this. If we kick this can down the road for a bit I bet all of our projects can benefit.