DINITROL RC800 rust converter is a milky emulsion which converts hard rust into a stable organic iron complex and requires a primer prior to over-painting, whereas DINITROL RC900 is a rust converter and primer. RC900 contains a complex organic chelat base and epoxy resin actively converting the rust. Once dry, an impermeable barrier against further corrosion is formed. DINITROL RC 900 penetrates rust 7 to 10 times deeper than standard rust converters. Free of lead, zinc and chromium.