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  #1  
Old 06-04-2019, 04:38 PM
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Painting Magnesium valve cover

Hi all,
Looking for opinions and experience acquired refinishing magnesium engine valve covers. These were common on M103, M104 and possibly others.

The research indicates that magnesium requires specialized treatment and/or specialized finishes, and not your common variety engine paint. In any event, I had refinished my M104 cover about 5-6 years ago, but some bubbling and popped paint chips have reared their ugly heads yet again. LuckilyI scored a very good shape spare at the picknpull and am considering a more permanent refinishing.

From what I've read there seem to be 2 prevalent approaches to refinishing magnesium, the most traditional being a combo alkaline wash, chromic acid treatment, followed by zinc chromate primer and paint. Unfortunately the chromic acid is hard to find, and is nasty stuff to handle. The zinc chromate paint etc. is easy to obtain.

The second approach that several wheel refinishers recommend is using etching primer followed by 2k primer/paint.

What have you done and found to hold up well over the years?

TIA
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Old 06-05-2019, 11:59 PM
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your request reminded me of other folks wanting to bling their intake manifold made of
similar material

one
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Old 06-06-2019, 07:04 AM
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I would just clean the inside,but out side is ok to do.I used caliper paint for heat
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Old 06-06-2019, 08:51 PM
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I used a high heat wrinkle paint on mine. So far seems to have no issues




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Old 06-06-2019, 11:41 PM
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If you can get it VHT make a decent primer and various high temperature paints

(Their caliper paints are especially good)
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Old 06-07-2019, 05:24 AM
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back in the 125 hp wet shot days
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Old 06-07-2019, 08:21 AM
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I tried a few times with different brand stuff, never got it to hold more than a year or two. Very difficult to find a powder coater even.

C4 Vettes had same mag covers, well at least TPI did. I heard lots of Japanese bikes do as well as some vintage Porsche.

In for info! I hate my nasty cover on the M103
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Old 06-07-2019, 12:36 PM
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I wasn't previously aware that the M103 cam cover is magnesium. Some years ago I researched magnesium finishing for a friend who got tired of polishing the Halibrand magnesum wheels on his Safir GT-40. Just siting in the garage the polished wheels would rapidly degrade to a dull, "fuzzy" looking finish due to oxidation and looked terrible.

I contacted friends still in the aerospace industry but came up blank. Helicopter gearbox casings are often magnesium, but apparently they are just left bare.

My M103 valve cover started to develop a few bubbles and now has more and a few breaks. The coating is very thick and I'm not sure it's paint, but maybe some kind of liquid plastic, and I think it serves to attenuate valve train noise in addition to improving cosmetics.

I know some vintage Porsche flat-sixes have magnesium cylinder case halves, but I'm not aware that they are anything other than bare. Of course you can't see much of a Porsche engine when you open the engine cover, but on a M103 Merc that big cam cover dominates the view.

If anyone knows of an "industry standard" way of finishing magnesium, if such exists, I'd sure like to know.

Duke

Last edited by Duke2.6; 06-08-2019 at 10:20 AM.
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  #9  
Old 06-07-2019, 04:56 PM
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Thanks for the suggestions, and keep them coming.

Nice job speednjay and oldsinner, thanks for sharing both look great. Speednnay, I had considered the wrinkle paint, did you use a bonding agent or special primer?

Ive been to some paint suppilers, automotive and aerospace and still not getting a clear direction, everyone agrees its a challenge and offer some excellent bonding enhancers but the industry is mostly tailored to aluminum. The aerospace folks have been indicating to treat like aluminum and just be prepared to do it over in several years. Kinda hoping for better than that.

FWIW. I have been treating the exposed spots of magnesium with zinc paint, eastwood tanktone, and this has held up remarkably well for about a year. To early to make a long term assessment. Possibly a zinc based primer is the way to go with a high heak 2k topcoat as suggested???
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Old 06-07-2019, 06:27 PM
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High heat paint is unnecessary for a valve cover. This is last one I did. Has been holding up for a couple years. Primed with adhesion promoter and used regular Rustoleum satin and top coat with alternating coats gloss and flat clear because I didn't have any low-sheen.

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Old 06-07-2019, 07:08 PM
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I didnít do anything special. Just a light prep and cleaning then sprayed. It may hold up or Iíll have to respray it down the line. No big deal. I rattle canned my 606 diesel cover the same way and lasted years till I sold the car.
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