Continuous coil pretreatment process

A continuous coil pretreatment process comprising:

• a) cleaning a surface of an aluminum sheet or a coil by water spray impingement;
• then
• b) etching the surface of the aluminum sheet or the coil by spraying the surface of the aluminum sheet or the coil with an acidic etching solution comprising about 1.5 to about 10 vol. % of sulfuric acid for a period of about 5 seconds to about 15 seconds, wherein the acidic etching solution in contact with the surface of the aluminum sheet or the coil is controlled to maintain a concentration of aluminum and magnesium ions not exceeding 1,000 ppm and wherein the acidic etching solution is replaced or replenished when the concentration of aluminum and magnesium ions exceeds 1,000 ppm;
• then
• c) rinsing the surface of the aluminum sheet or the coil with deionized water at a temperature of about 37° C. to about 65° C.;
• then
• d) applying to the surface of the aluminum sheet or the coil a solution comprising a vinylphosphonic acid-acrylic acid (VPA-AA) copolymer for a period of about 5 seconds to about 20 seconds, wherein a concentration of the vinylphosphonic acid-acrylic acid (VPA-AA) in the solution comprising the vinylphosphonic acid-acrylic acid (VPA-AA) copolymer is about 0.8 wt. % to 1.0 wt. %;
• then
• e) rinsing the surface of the aluminum sheet or the coil either immediately after step (d) or with a delay of about 1 second to about 5 seconds, wherein the rinsing comprises (i) spraying the surface of the aluminum sheet or the coil with deionized water in a spray direction opposite a feed direction of the aluminum sheet or the coil as it advances in the continuous coil pretreatment process, (ii) providing a water dam at an entry point of an exit squeegee roll, and (iii) continuously rinsing a surface of the exit squeegee roll;
• and then
• f) drying the surface of the aluminum sheet or the coil.