Thread: What sanders to use to sand back this treated pine outdoor bench

are you trying to change the look of it or refresh the finish?

As if it were me i'd give it a good sanding with an RO sander, mostly to scuff up the surface. Clean it with some sugar soap, let it dry and sand it once more time with a higher grit paper. Then reapply finish.

If its treated i'd want to be sanding as little of it as i can get away with.

If you're attempting to restain or similar i'd use a belt sander or use planes/scrapers to get the bulk of the finish off before sanding

Something powered with a 60-80 grit belt or disk. Make sure you have good breathing protection as you don't want arsenic bearing pressure treatment residues in your lungs.

You have to get all that finish off before you reapply. UV causes it to fail at the timber/finish interface.

I'd remove the old stuff with a tungsten scraper - a quick job - then a light attack with the ROS with 180-200 grit. Then 2 or 3 coats of new finish.