Metal pretreatment composition containing zirconium, copper, and metal chelating agents and related coatings on metal substrates

A method for improving paint adhesion to a metal substrate that is subjected to a pretreatment with a zirconium-based pretreatment coating composition comprising the steps of:

• a) contacting a metal substrate with a pre-rinse comprising a copper chelating agent, and optionally copper, prior to application of a zirconium-based pretreatment coating composition to the metal substrate;
• b) applying to the metal substrate a zirconium-based metal pretreatment coating composition comprising dissolved Zr, a source of fluoride, optionally materials comprising one or more of silicon, boron and yttrium and optional added dissolved Cu, wherein the composition has a pH in the range of 6.0 to 9.0, thereby forming a pretreatment coating on the metal substrate;
• wherein the copper chelating agent is present in the pre-rinse in an amount sufficient to control the amount of copper deposited onto the metal substrate by the zirconium-based pretreatment coating composition such that the average total ratio of atomic % of Cu to atomic % of Zr in the pretreatment coating deposited on the metal substrate is equal to or less than 1.1.

A zirconium-based metal pretreatment coating composition comprising water and dissolved Zr, a source of fluoride, a copper chelating agent, silicon, added dissolved Cu, and one of boron or yttrium.

A zirconium-based metal pretreatment coating composition comprising water and dissolved Zr, a source of fluoride, a copper chelating agent, silicon, optionally materials comprising one or more of boron and yttrium, and optional added dissolved Cu.