Curable, weldable coating compositions

An aqueous-based curable coating composition comprising:

• a. a resinous binder comprising
• i. a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
• ii. a curing agent having functional groups reactive with the functional groups of (i);
• b. an electroconductive pigment dispersed in (a) such that the weight ratio of b to (i) plus (ii) is within the range of 0.5 to 9.0:1;
• and
• c. water,
• the coating composition being characterized such that when it is deposited and cured on a metal substrate, the cured coating is weldable.

An organic solvent-based curable coating composition comprising:

• a. a resinous binder comprising
• i. a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
• ii. a curing agent having functional groups reactive with the functional groups of (i);
• b. an electroconductive pigment dispersed in (a) such that the weight ratio of b to (i) plus (ii) is within the range of 0.5 to 9.0:1;
• and
• c. an organic solvent,
• the curable coating composition being characterized such that when it is deposited cured on a metal substrate, the cured coating is weldable.

A process for coating a continuous metal sheet comprising:

• a. applying directly to the metal sheet shortly after it is formed and at a temperature of 20 to 1 50° C., a curable coating composition comprising:
• i. a resinous binder comprising
• (A) a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
• (B) a curing agent having functional groups reactive with the functional groups of (A);
• ii. an electroconductive pigment dispersed in (i) such that the weight ratio of (ii) to (A) plus (B) is within the range of 0.5 to 9.0:1,
• the curable coating composition being characterized such that when it is deposited and cured on a metal substrate, the cured coating is weldable;
• and
• b. drying the coating composition on the metal sheet.

A process for coating a continuous metal sheet comprising:

• a. unwinding the metal sheet from a metal coil and passing the metal sheet in a substantially continuous manner through a cleaning station, a coating station, and a curing station;
• b. applying to the metal sheet at the coating station a curable coating composition comprising:
• i. a resinous binder comprising:
• (A) a reaction product of an epoxy-containing polymer with a compound containing phosphorus acid groups, the reaction product having reactive functional groups,
• (B) a curing agent having functional groups reactive with the functional groups of (A);
• ii. an electroconductive pigment dispersed in (i) such that the weight ratio of (ii) to (A) plus (B) is within the range of 0.5 to 9.0:1;
• and
• c. curing the coating composition applied to the metal sheet in step (b) as the coated metal sheet passes through the curing station.