Found a wild fact about blending aluminum panels yesterday

I was reading through some old auto body forums late last night and stumbled on this stat: apparently, aluminum panels can form micro-cracks just from being sanded too aggressively if the grit is under 80. I always figured harder metal meant tougher, but it's the opposite. Found this nugget on a thread from a guy who used to work for Ford's collision program back in 2016. Has anyone else run into weird material limits like that where the common sense approach was totally wrong?

2 comments

2 Comments

patriciaellis1mo ago

That bit about grit under 80 wrecking aluminum panels rings a bell. My buddy Rob was restoring an old F-150 and sanded the hood with 60 grit to strip paint fast. The whole thing was covered in hairline cracks afterward, looked like a spiderweb in the sun. He had to buy a whole new hood because the metal was compromised.

barbarahill1mo ago

And then the real kicker with aluminum is that even if you don't see cracks, the heat from the sanding can mess with the temper. I had a buddy who worked in a body shop back in the day, and @patriciaellis's story about that F-150 reminds me of a similar issue he ran into with a late-model Audi hood. He tried to work out a dent with a heavy hammer and dolly, thinking it was steel, and the whole panel ended up with stress fractures around the edges. Common sense says bang out the dent but with aluminum you basically just made the whole thing scrap. It's like the metal punishes you for treating it like regular old steel.