Sand blasting engine parts, again...

Hi everyone. Some time ago I posted questions about my engine renovation and particularly about sand blasting engine parts. It's going well and I am blasting away at all parts that are not related to sensitive systems, like fuel.
Now I have come to the gearbox, which is severely corroded after having been submerged in salt water. See picture. I can take it off from the bell housing that it is attached to now, but then what? Putting it in the blaster cabinet seems stupid, as there are bearings between the gearbox and the shaft coupling that comes out of it, and I cant protect that from flying sand. What method would you use to clear this from all the horrible white and grey stuff?

 

Blast away, replace bearings afterwards.
They’ve been submerged, should be replaced anyway.

 

It is difficult without being able to hold and turn things, but some castings might be getting thin with the amount of corrosion. It might pay to look further, and if the gearbox will come apart then bearings can be cleaned and inspected prior to reinstallation or replacement. It should have a seal kit really anyway. kapnD bearings might be ok if the seals and o-rings remained intact.

 

Anytime I have one on the bench, it’s getting new seals at the very least!

 

For sure, and whatever else it needs. I meant that the seals weren't breached during the sandblasting, I tend to abbreviate when I'm in a hurry sorry. I have not had one of those apart so have no idea if they need factory tools for setting up. Certainly a lot of manufacturers try to keep things proprietary when they can.

 

Ok, thanks for the input. I am hoping it is still ok and I will open it up and have a look, seal replacement in hand. It ran smoothly before I took oit off and the oil is not brown or grey. Will get back with details and photos. Thanks for now. More opinions are wellcome.

 

I would chose a medium that is not harder than the underlying substrate rather than sand.
Walnut shells should work for this application. The advantage is not having to deal with abrasive grit getting into sensitive wear areas
You will still have to mask off bolt head flats/bosses etc. A soft tape will suffice or install bolts through the holes with an oversize flat washer to protect these areas.
The video below discusses various mediums.

You might also find a company that has a dry ice blaster which uses granulated dry ice pellets. The dry ice evaporates/sublimates leaving only the material that has been blasted off. Googling Dry Ice Blasters in your area will more than likely find a company who could do this. There are also laser cleaners as well.

No matter what you use, the surface will be very rough due to the corrosion with peaks and valleys/troughs on the surface. I expect that you will repaint. Do not use a simple paint in a spray can as the mil build up will not be enough to fill the valleys and cover the peaks, resulting in further corrosion in the very near future.

Some options:
Option 1
1) Walnut blast
1a) polish the surfaces to minimize the peak to valley number in the coarse corroded area
2) re -walnut blast ( remove the bolt flat abrasive tape and at low velocity, lightly walnut blast these areas) A quick wash with a solvent to get rid of any oil residue. Brake Clean, toluene, TriChloro, use in a well ventilated place)
3) apply a pre-primer, a slow drying product to ensure as much adhesion as you can. (not fast drying red oxide primer)
4) apply a thicker primer which will ensure that the valleys are filled and the peaks are covered to the manufacturer recommended thickness (not fast drying red oxide primer)
5) paint with at least 2 coats of a finish coat ( 2 coats to ensure that pinholes created by the solvents flashing off will be minimized)

Options 2 ( I expect there are others)
Apply some type of expoxy paste, thin enough to manipulate into all the surfaces to fill the valleys to smooth out the peaks. I imagine that there are others with epoxy experience to
offer guidelines