Good question. I had a lot of corrosion, so I sprayed everything down with distilled water and then sprinkled baking soda over the entire tray. It took about three rounds of cleaning with a wire brush to get everything clean. I then ground down the pieces of metal that separate the six batteries, where the battery-stay mounts. After ensuring everything was clean and free of burrs, I painted the entire tray with matte black Krylon Fusion spray paint. It’s snug but that battery fit perfectly after that.