Clear-coat on magnesium

I want to polish some magnesium engine casings. I know they will corrode in a very short time. Does anybody know if clear-coating them will prevent this, or am I just wasting my time?

Depending on the alloy, the magnesium may not polish well. With the old magnesium rims like Halibrand or Ansen, they would polish well so you may want to search what people did with those. A 2 part epoxy would hold up, but might not look as polished. I know guys use lacquer a lot because it's shinier thin, but it doesn't hold up as well.

Short answer, Yes it will seal it from the atmosphere and prevent corrosion.