Posted by dannparks on Sunday, April 19, 2009 @ 02:15 AM:
Any experiences out there in painting the VW magnesium engine case? Great Plains suggests using a 50-50 mixture of enamel paint and gasoline! Yeow! Does this really work? Does regular engine paint not stick? Does it make any sense to paint it, or will the paint just all come off eventually?
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Posted by eugenio on Sunday, April 19, 2009 @ 01:20 PM:
Painting the magnesium case will protect the case from corrosion, especially on salty locations (near the sea).
On all engines overhauled by me I use the following procedure:
1) Assemble the short block (engine without cylinders and accessories)
2) Clean it with acetone or nitrate thinner and air dry, mask any hole and everything you do not want painted. Mask the pushrod tube sealing surface on the case, the cylinder mating surface on the case and everything where
3) Apply one light coat of wash primer (best are primers specifically for Aluminium)
4) Apply one coat of polyurethane enamel (the colour you wish, dark is better)
5) Clean and paint the cast iron cylinders with black high temperature paint
Now you can proceed with the final assembly.
Advice: no paint between case and cylinder base, no paint below bolts and nuts and everything that must be torqued or you will loose your torque due to paint collapse between the parts.
Enjoy with your new engine!
ciao
Eugenio
Posted by dannparks on Sunday, April 19, 2009 @ 01:31 PM:
Thanks for the great info Eugenio. Do you just leave the heads unpainted?
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Posted by eugenio on Monday, April 20, 2009 @ 09:53 AM:
Yes usually heads remain unpainted, but in one case I painted the heads too, with the same process than the case with primer and enamel, and they are still painted after 300+ hours. Heads are less prone to corrosion than case, due to the different material.
ciao
Eugenio
Posted by milnerd on Monday, April 20, 2009 @ 10:22 AM:
I painted the magnesium crankcase of the LOM 137A engine in my Zlin about 4 years ago and it is still perfect. I did quite a bit of research before I started out. Having lived with it now I would do the same thing again.
I started out with bead blasting to bare metal with plastic media to avoid any chance of a spark. I then immediately used Magnadyne to etch the surface (it goes a dark brown colour). This is washed off with water after 10~20 minutes of keeping the surface wet with eth Magnadyne solution. After it was allowed to dry thouroughly this was followed with a two coats of two part epoxy primer and top coated with two coats of a water based grey epoxy enamel designed for industrial machinery. These were all applied with a brush. The LOM exterior surface is quite rough - as removed from the sand casting moulds with the flasing cleaned off and smooth machined areas where they need to be. I was careful to use only cadmium plated nuts, bolts and washers (stainless steel is terrible - the magnesium becomes a sacrifical anode for it). I also used a thick corrosion inhibiting spray coating (Corroshell 400 I believe) to fill the space between every stud and the washer under all the nuts. There is now no place for the electrolyte (moisture) to get between the steel stud, magnesium block, and cadmium plated hardware and get a galvanic cell going. To date no white fuzz anywhere, and perfect paint adhesion. My hangar is not insulated and can get very damp on those foggy days following a cold spell where everything just drips condensation.
Posted by eugenio on Monday, April 20, 2009 @ 10:44 AM:
Nice, but bead blasting the case is not a safe job because you risk to leave some media in oil galleries where yo will hardly have the possibility to remove it. If you need to remove the old paint you should put the case in heavy degreaser/paint remover like methilene dichloride, then clean it with acetone or nitrate or (bad smelling) MEK.
Eugenio
