So I’ve started the cleaning up of our propeller shaft. It had some brown gunk (like a dried muddy residue from corrosion) but no rust of itself.
However, in a number of places it has uncovered pitting. This seems to be concentrated on the bits that were just outside the various bearings etc. So the taper for the propeller itself is clean. The section where the cutlass bearing goes is clean although it looks as if the pitting at the inboard might have been made worse by a worn cutlass bearing causing some damage. There is also pitting around where the stuffing box was, fortunately the dripless seal will be in one of the cleanest sections.
So far I’ve used a strip of 150 grit emery cloth. I’ve got 3 other grades upto 400 grit, so we will go over it with all of them. In all cases we are sanding round the shaft not up and down the length which is apparently important for the seal.
Just wondering whether we need to do anything about the pitting. Chemicals? More sanding? Or what?
Also what caused it. Was it the poor grounding causing galvanic/electrolytic corrosion? Is it something to do with the bearing?
Anyway here is a gallery of pictures of the pitting. What do you think?