| abstract |
In a process for coating an electrically conductive substrate, the substrate is immersed in an aqueous bath based on a synthetic resin binder neutralized at least in part with acids and containing cationic amine and / or hydroxyl groups. , as well as a mixture of crosslinking agents, pigments, fillers, anti-corrosives, lacquering adjuvants, where appropriate catalysts, and up to 15% by weight of the total weight of the coated with an organic solvent. The substrate receives a direct current as a cathode, which causes precipitation of a film on the substrate. The substrate is removed from the bath and the film is cured by baking. The mixture of crosslinking agents contains at least two crosslinkers based on activated esters and / or containing polyisocyanates blocked by different blocking agents. These crosslinkers have different reactivity, that is, upon heating, their crosslinking reaction begins at temperatures which differ by at least 10oC. The crosslinker which reacts first constitutes between 15 and 60 mole percent of the mixture. The first coating layer is rinsed, and before firing one or more additional cathodic coatings are carried out. The coating layers are rinsed one after the other, then hardened all together. |