Electrodepositable coating compositions and processes related thereto

A process for coating an electroconductive substrate comprising the following steps:

• (a) electrophoretically depositing on the substrate a curable electrodepositable coating composition to form an electrodeposited coating over at least a portion of the substrate, the electrodepositable coating composition comprising a resinous phase dispersed in an aqueous medium, said resinous phase comprising:
• (i) one or more ungelled, active hydrogen-containing cationic salt group-containing resins which are electrodepositable on a cathode;
• (ii) one or more at least partially blocked polyisocyanate curing agents;
• (iii) at least one substantially non-volatile antioxidant;
• (iv) at least one volatile antioxidant;
• and
• (b) heating the coated substrate of step (a) in a curing oven at a temperature and for a time sufficient to cure the electrodeposited coating on the substrate.

A curable electrodepositable coating composition comprising a resinous phase dispersed in an aqueous medium, said resinous phase comprising:

• (a) one or more ungelled, active hydrogen-containing cationic salt group-containing resins which are electrodepositable on a cathode, said resins selected from at least one of an aromatic polyepoxide comprising amine salt groups, and aromatic polyepoxide comprising sulfonium salt groups, a vinyl polymer comprising amine salt groups, a vinyl polymer comprising sulfonium salt groups, and mixtures thereof;
• (b) one or more at least partially blocked aromatic polyisocyanate curing agents;
• (c) at least one substantially non-volatile antioxidant;
• and
• (d) at least one volatile antioxidant selected from at least one of n-propyl 3,4,5-trihydroxybenzoate, 1,2-dihydroxy-4-tert-butylbenzene, 2-isopropyl-5-methylphenol, 3-tert-butyl-4-hydroxyanisole, butylated hydroxytoluene, and hydroquinone monomethyl ether.

A process for coating an electroconductive substrate comprising the following steps:

• (a) electrophoretically depositing on the substrate a curable electrodepositable coating composition to form an electrodeposited coating over at least a portion of the substrate, the electrodepositable coating composition comprising a resinous phase dispersed in an aqueous medium, said resinous phase comprising:
• (i) one or more ungelled, active hydrogen-containing cationic salt group-containing resins which are electrodepositable on a cathode, said resins selected from at least one of an aromatic polyepoxide comprising amine salt groups, and aromatic polyepoxide comprising sulfonium salt groups, a vinyl polymer comprising amine salt groups, a vinyl polymer comprising sulfonium salt groups, and mixtures thereof;
• (ii) one or more at least partially blocked aromatic polyisocyanate curing agents;
• (iii) at least one substantially non-volatile antioxidant;
• (iv) at least one volatile antioxidant selected from at least one of n-propyl-3,4,5-trihydroxybenzoate, 1,2-dihydroxy-4-tert-butylbenzene, 2-isopropyl-5-methylphenol, 3-tert-butyl-4-hydroxyanisole, butylated hydroxytoluene, and hydroquinone monomethyl ether;
• and
• (b) heating the coated substrate of step (a) in a curing oven at a temperature and for a time sufficient to cure the electrodeposited coating on the substrate.