Painting engine parts

I am taking apart a Volvo MD2010 from 2006 that has been damaged by salt water. See my other post about issues removing the driveplate in the flywheel. I am not stripping the engine down completely, just taking off parts for repainting, and I am leaving the main engine block, cylinders etc in place.
Anyhow: as I take bits and pieces off to have them repainted some questions arise:
I have access to a sand blaster - are there any reasons not to sand blast engine parts? Obviously this would be lose parts that I can take off, completely free of cables, rubber seals etc. Only steel of aluminium. But should I be mindfull about jointing surfaces, like for example the heat exchanger housing, that has a surface against the main engine block?
Inevitably someone will ask me why I want to sand blast - it seems a fun and efficient way to get rid of the old paint.
The alternative of course is to peel off any loose paint and then give it a good sanding and renew the paint job, but stripping completely would allow me to scorch the surfaces with a blow torch in order to get them free of all contamination before repainting.
Lastly: a lot of parts on this engine is aluminium. Couldn't I just sprip them of paint and leave them bare? Does painting aluminium do any good at all? I seem to remember someone saying that aluminium is best left alone to form its own oxidization layer and that paint does nothing to protect it.

And even more lastly: someone I talked to suggested that when stripping an engine of paint, one could just as well leave it bare completely, and just keep it smeared in a thin layer of linseed oil (or the like). The idea would be that paint inevitably flakes off anyway. Or maybe he was just being excentric. Anyway I leave his opionion here for anyone to comment on.

 

I have sandblasted many engines and parts. Mating surfaces should be taped over to protect the surface. 2 or 3 layers of duct tape and some common sense is all it takes. Aluminum can be left unpainted, but will eventually turn a dull gray. Linseed oil will make a mess and won't last long. Paint only flakes if it wasn't done correctly. Sandblast, prime and paint. It will last many years. Industrial alkyd enamel is all you need.

 

Thank you Gonzo! My intuition was right then. And how about that advice to scorch the parts with a blow torch to bring out impurities to the surface before painting? Is that adviced?

 

Yes, damage.
You'd be far better off glass beading the pieces.
Both are surface treating which can reduce surface cracks considerably.
If you only have access to SB, be very, very careful.
High heat enamel ( white if you can find it ) is fantastic over primed SB or GB treated steel.
Don't paint the aluminum, just leave it bare after surface treating.

Pictures?

 

I have done as Gonzo suggests many times.

I suggest clean (acid bath or particle blasting), thorough degrease, mist coat of single pack acid etch primer, then would use an engine enamel, thinned, through a spray gun over cast iron and aluminium. Remember lungs, ears and eyes during this work.

 

Everybody here in Sweden seem to go for, and recommend, Hammerite. They promise "no primer needed", which allways makes me suspicious. Any opinions?

 

If everyone is using it and it works...

 

Hammer finish paint covers a multitude of sins, but nothing will stay on bare aluminium without etch primer. Nasty stuff to use however.

 

Well, I was just wandering whether Hammerite is a good product for the steel engine parts, or if I should look around for something else. Also, in the workshop where I am a member we have the possibility to powder coat, with oven and all. But I doubt that I will find the Penta-green colour in powder. I will leave the eluminium parts unpainted I think.

 

The hammer paint will be fine, goes through a spray gun like any other enamel.