"Vinyl wash" is a very thin etching primer. It has a PVC in it ( the "V" in PVC is "vinyl") and gives the highest in corrosion protection. It is different in that you can't paint over it, it is only about .5 mil. Where a regular etch prime would be up to 1.5 mil as applied. All it takes is one medioum coat, very fast appication. It has no body to it and looks transparent, but does its job.
