Hello,
Based on a groundswell of interest (one personal message), I thought I would share the process for getting my gearbox cover from pitted and corroded to a decent (in my opinion) state of shine. I suppose, and hope, that this topic will draw the attention of those needing helpful ideas to make it easier next time.
In the first photo you can see the gearbox cover with an overall patina of corrosion and a very pitted portion that looks like it had been partially sitting in mud (or something).
The second photo shows the completed process.
In the third photo you can see some dings I felt were too deep to try to remove, as it would mean taking the entire surface down to the bottom of those dings and, maybe, making the wall thickness too thin.
In the fourth photo you can see two of three power sanding approaches I used. First was the 60-grit disk in a hand-held drill motor to take out the corroded pitting and any raised up areas around deep nicks. An easy hand is required here, as you could create some deep gouges before you knew it. I did not use this wheel all over the cover, as it makes it's own deep scratches which must be removed. Of course, one could forego power sanding entirely if the first cleanup could be reasonably accomplished by hand sanding. In any case), start with the finest grit you can get away with while getting the job done in this millenium.
After the course wheel, I put the 80-grit flapper-type sanding device in the drill motor clamped to the bench and used it pretty much all over the cover where it would reach. It did good job attacking the scratches from the disk, removing most of the overall corrosion and rounding-over any ridges left by the disk. This was the first time I had used one of these flapper sanders and I was surprised by how controllable it was even though the grit was fairly course.
I had also tried a sanding disk in a Dremel tool, but found that when removing any noticeable amount of material it left a lot of little scallops. So I gave up on that. I probably just didn?t have the right technique.
After the power sanding I started in with hand sanding, using the papers I had on hand, and using wet sanding when that was the paper type. The grits were as follows: 120 (dry); 150 (dry); 220 (wet); 320 (dry); 400 (wet); 800 (wet); 1000 (wet). As grits get finer the paper is folded more to make a durable tool of it and to distribute the force applied by your thumb. For each grit you sand the whole surface until the scratches for that grit are the deepest ones seen.
In the fifth photo you can see my two buffing wheels. After the last sanding I used a 6", tight-sewn, buffing wheel as available at the hardware store. I don't have a legitimate buffing machine (long shaft and unshielded wheels), so it went in my bench grinder. The access to the wheel was just enough to reach all over the cover. For the first pass I used my more worn (stiffer) buffing wheel with Dico Tripoli TC6 (Brown), general cutting, buffing compound. For the last pass I used a new buffing wheel with Ryobi "H" White Rouge polishing compound. (I'm not showing the picture of the compounds due to having reached the posting limit.)
Apologies to any or all of you who have read this far, only to learn that you didn't learn much and that I am a great-big-bodger. If it does help anyone, I'm glad. I type reasonably fast, so wordiness is an easy crime.
Richard L.
