To prolong the service life of a self-depositing resin bath by bringing a specified percentage of the total amt. of a used self-depositing resin bath contg. dissolved Zn and Fe ions into contact with a cation exchange resin, then bringing the bath into contact with the surface of an Fe- or Zn-base metal and forming a coating film on the surface of the metal.
At least 30% of the total amt. of a used self-depositing resin bath is brought into contact with a cationic resin having cations of at least one of H and Fe bonded reversibly without adding a dispersant. The bath is then brought into contact with the surface of an Fe- or Zn-base metal and a coating film is formed on the surface of the metal. The cationic resin is a cation exchange resin having functional groups such as iminodiacetate groups or aminophosphonic acid groups and dissolved Zn cations are transferred to the cation exchange resin and substd. for H or Fe ions.
KURISUTEIINA EMU HAASU
BASHIYAA EMU AAMEDO
