Method of bonding phosphated steel surfaces electrodeposited with a primer

A method of adhesively bonding together surfaces of two automotive steel components where at least one is phosphated and electrodeposited with an organic primer comprising the steps of:

• applying to at least one such surface a heat curable two-part epoxy adhesive where the adhesive resin comprises in parts by weight 100 parts of a cross-linkable epoxy novolac resin having an epoxide equivalent weight in the range of from 150 to 200 and a viscosity at 50.degree. C. in the range of from about 1000 to 2000 centipoise;
• from about 40 to 60 parts of an aliphatic epoxy reactive diluent which is the reaction product of a trifunctional alcohol and an epichlorohydrin having an epoxide equivalent weight in the range of from about 130 to 170 and a viscosity at 25.degree. C. in the range of from about 120 to 240;
• from about 11 to 16 parts of imidazole curing agent substituted in at least one position with an alkyl or a hydroxyalkyl group;
• pressing and holding the two steel components together wherein said adhesive forms a bond between surfaces of said steel components of at least about 15,000 joules per square meter when the adhesive is cured at 200.degree. C. for 25 minutes and tested at 25.degree. C.;
• said adhesive retaining a bond strength of at least about 12,000 joules per square meter when tested at 25.degree. C. after 8 weeks continuous exposure to 5% sodium chloride salt spray solution at 37.8.degree. C., and after 7 days immersion in water at 60.degree. C.