We have an application that will involve spotwelding 7075-T652 to 6061-T6. The parts are alodined. The customer wants to have the interface alodined prior to spotwelding to insure this area is coated and to preclude any bleedout that would happen if done later. We have done some sample schedules and have met tensile strengths, nuggets are OK. We have had small surface cracks which were not visible until after alodine touch-up. I would like to minimize these by adjusting the forge pressure and current decay. Normally we allow no coatings on our aluminum and have it chemically etched so this is something new to me and I have been unable to find anything in my literature. I would like to know if I'm on the right track or out in left field.
Thanks Bob