Originally Posted by
BTinNYC
Nothing. Bonderizing is not a coating, it changes the metal's surface through a process of phosphoric acid bath and heat.
According to the Parker Rust Proof trademark application there is a coating.
Justia - Parker Rust Proof
PARKER RUST PROOF COMPANY PROTECTED BY BONDERIZING CORROSION PROTECTION BONDERITE CHEMICALS - Trademark Details
Statements
Certification Mark Statement
THE MARK CERTIFIES THAT THE GOODS HAVE BEEN TREATED WITH MATERIALS SOLD BY PARKER RUST PROOF COMPANY UNDER ITS TRADEMARK "BONDERITE" TO PROVIDE A HIGH QUALITY CORROSION RESISTANT PAINT HOLDING COATING.
Edit:
Parkerized has a coating.
See page 66 of "Sweet's catalog file : sections 1-7."
Sweet's Catalog file: Section 1-7