Q. How can I remove the factory coating from a 1972 ford truck aluminum grill shell so I can re-polish it? When I start sanding the old finish, it seems to have been coated from the factory. S.A.
A. The first thing I would do is confirm the part you are trying to finish is actually aluminum. The vehicles of the 1970s were known for their size and lack of fuel efficiency. Cost was important at the time, so I would have thought it may be a steel alloy. Simply take a magnet to it. If it is not magnetic, it is not mild steel, so your assumption regarding base metal is probably correct.
Regardless of the base alloy, it’s likely there was a coating of some sort on the grill when it rolled off the factory floor. It is probably coated by plating, painting or clear coating of some sort. Without knowing the type of coating or its chemistry, it is difficult to recommend a stripping solution or chemistry. (Another reason it’s good to know the base metal.)
You would probably be more successful if you were to have the coating removed by media blasting. Unless the depth of the grill is too great, the blasting gun should be able to aim from different oblique angles in order to remove the coating from all surfaces.
Choice of blast media will be important. Something?hard like sand may “bite” into the base material too deeply. Alternatives would be plastic media blasting and glass bead. The plastic media used is available in a variety of geometries, sizes and hardnesses. The media manufacturer would likely be able to recommend a way to optimize success with the coating removal and minimize base metal attack.
Good luck with your restoration project.