21-Aug-2011 Going Green! The boiler in green etching primer. I had spent the previous day going over the boiler with a 40-grit flap disk on the angle grinder removing all the dirt, paint and more importantly, rust. Everything else on the locomotive is protected with a layer of paint, why not protect the single-most expensive item -- the boiler? What a mess all that dirt and rust and mill scale made in the shop, everything is covered with a layer of grime.