For better or worse, I chose to paint the inside of our oil filter canister with Glyptal insulating enamel. They call it Glyptal red, but it’s really more of a Golden Gate orange to me.
I bead blasted the outside of the canister, and took steps to prevent any media getting inside. I basically stuffed foam earplugs into the ports and taped over them. Even with that, I didn’t have 100% confidence nothing got inside. The Glyptal is designed to seal the tiny pores left in metal after bead blasting, and leave the engine block interior smooth and clean for improved oil flow.
If it’s good enough for the oil breather / filler can, it seems like it should be appropriate for the filter canister too.
Please ignore my high-tech paint booth comprised of the trash cans on the side of our garage.
