Paint prep for cast iron blocks and ally gearboxes

[rolesyboy]

For longevity what do folks find is the best way to prep
1) a cast iron block for paint
2) the associated ally parts like gearbox, flywheel housing etc

I almost always acid dip the block and have the ally casings cleaned up properly.
Do people use a primer of any sort and what are the results like after say a years worth of heat cycles?
I hand paint mine but always looking for a better way.
Cheers
Mark

[Peter Laidler]

I can only comment on aluminium allots Roly.....
Glasurit-Beck, the Dutch paint makers, who used to have a training school here in Abingdon (and who painted my S for me, as a training project) told me when I asked the same question, was that the best treatment for all aluminium alloy was to strip the wheel or whatever down to either a) bare metal OR to where the previous paint was still intact and adhering properly. Then prime in a sort of wishy-washy yellow tinged called zinc-chromate. Allow to cure and two-pack colour.

Their experience in this field was Concorde wheels, Navy helicopter wheels and winch-gear that was continually salt water saturated.

Nice people

[Spider]

On the Cast Iron, I just use a primer and then enamel paint, the slow drying type I found is much better than the quick dry.

Aluminum and alloy is pretty difficult to paint I found, nothing lasts long term and of course, when it starts to flake off, it makes the gearbox look really rough. Powder Coating does work exceptionally well though, but to do a gearbox this way means loads of masking. I'll get one anodised one of these days to see how that goes. I leave mine bare, though when left like this then need to be kept clean to avoid corrosion.

[Nick W]

Engine blocks are often soaked in engine oil after any engineering work, it's surprisingly difficult to remove it all before painting , steam cleaning works, but you have to get it dry quick before painting it. Once painted it can be re oiled up.

[Jason]

A coat of ACF50 works really well on bare aluminium and other metals. Used a lot for aircraft and marine applications, not cheap but well worth using.

[minibitz]

I use colour matched spray enamel when doing BMC green or VHT engine enamel for all other colours. I don't use a primer and to date have not had an issue with flaking.

The trick is to get the surface spotlessly clean first. I'm usually painting engines that have had block, head and gear cases chemically dipped. I give them a couple of good blasts with brake cleaner, then blow down with an air line. The brake cleaner really does rip of any residual oil and grease, even on a dipped component that already looks spotless!

[rolesyboy]

Thanks Jason. Not seen that before. Is it a sticky finish or does it work like a clear laquer?

A coat of ACF50 works really well on bare aluminium and other metals. Used a lot for aircraft and marine applications, not cheap but well worth using.

[rolesyboy]

Engine blocks are often soaked in engine oil after any engineering work, it's surprisingly difficult to remove it all before painting , steam cleaning works, but you have to get it dry quick before painting it. Once painted it can be re oiled up.

Agreed. I usually have mine acid dipped so the journals are rust and crud free. Not always practical to get it turned around though especially if its a head rebuild or similar.

[rolesyboy]

I get stuff powder coated all the time and yet I have never considered that as an option for a gearbox or flywheel housing but I like the suggestion.
You sound very confident Spider. Should I go for it?

On the Cast Iron, I just use a primer and then enamel paint, the slow drying type I found is much better than the quick dry.

Aluminum and alloy is pretty difficult to paint I found, nothing lasts long term and of course, when it starts to flake off, it makes the gearbox look really rough. Powder Coating does work exceptionally well though, but to do a gearbox this way means loads of masking. I'll get one anodised one of these days to see how that goes. I leave mine bare, though when left like this then need to be kept clean to avoid corrosion.

[rolesyboy]

I can only comment on aluminium allots Roly.....
Glasurit-Beck, the Dutch paint makers, who used to have a training school here in Abingdon (and who painted my S for me, as a training project) told me when I asked the same question, was that the best treatment for all aluminium alloy was to strip the wheel or whatever down to either a) bare metal OR to where the previous paint was still intact and adhering properly. Then prime in a sort of wishy-washy yellow tinged called zinc-chromate. Allow to cure and two-pack colour.

Their experience in this field was Concorde wheels, Navy helicopter wheels and winch-gear that was continually salt water saturated.

Nice people

Thanks Pete. Another option

[Jason]

Thanks Jason. Not seen that before. Is it a sticky finish or does it work like a clear laquer?

A coat of ACF50 works really well on bare aluminium and other metals. Used a lot for aircraft and marine applications, not cheap but well worth using.

It does dry Mark on surfaces that get hot, it remains slightly sticky on cold surfaces. I still use it on my alloy wheels, a coat on before the salt starts, keeps the corrosion away

[Spider]

I get stuff powder coated all the time and yet I have never considered that as an option for a gearbox or flywheel housing but I like the suggestion.
You sound very confident Spider. Should I go for it?

On the Cast Iron, I just use a primer and then enamel paint, the slow drying type I found is much better than the quick dry.

Aluminum and alloy is pretty difficult to paint I found, nothing lasts long term and of course, when it starts to flake off, it makes the gearbox look really rough. Powder Coating does work exceptionally well though, but to do a gearbox this way means loads of masking. I'll get one anodised one of these days to see how that goes. I leave mine bare, though when left like this then need to be kept clean to avoid corrosion.

I've not heard of or seen the results of the ACF50 that Jason mentioned but that perhaps would be easier than Powder Coat, it does sound good and I think possibly easier than PC.

In regards to Powder Coating, my Blaster Man hates allow parts that have been powder coated, and it was him who first suggested to me how good it is. He hates it because it's so hard to get off by blasting. He laughs at it on steel because it does come off so easy, but on alloy and aluminum parts, he hates it.

A friend of mine did his clutch cover and a few other smaller alloy parts over 20 years ago, it's still all only there with no sign of flaking or budging.