|
Hi JKC, Sandblasting is the best prep for both castings and sheet steel. The problem with sandblasting assembled cast housings like gear cases and engine blocks is the risk of getting grit into the interior despite one's best effort at blocking up all possible paths. I can assure you (by past experience) that grit will get in places you never thought it could. However, when cast housings are completely disassembled and all the internals, seals, bearings, etc removed, you can visually observe the interior cavities and clean any grit out before it causes a problem. I suggest some type of solvent cleaning of the interior to remove oily films prior to blasting the outside simply to make it easier to clean out any grit afterwards. A dry interior makes it much easier to use compressed air to blow out small cavities and passages that are not readily visable - I'm thinking of cylinder heads here. As long as you can assure yourself there is no grit remaining anywhere in the interior areas, you should be fine to reassemble and paint. If it were mine, I'd also block the openings and apply at least one coat of epoxy primer to the exterior as a preservative during the time it takes for assembly. If assembly takes long enough to extend outside the recoat window of the epoxy, simply scuff with a Scotch-Brite hand pad, apply another coat of epoxy and topcoat within the window. The assembly process will likely get numerous fingerprints and possibly an oily residue on the exterior so a thorough cleaning with something like PPG's DX330 prior to any further epoxy or topcoat would be advisable.  Rod
|
