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Old 11-11-2005, 23:27   #1
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Engine Paint

One last question - for now

A few parts of my diesel have surface corrosion. I want to clean them up and paint them so it looks nice, and to stop the corrosion.

What paint do you use on a marine engine?

Thanks,

Craig
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Old 12-11-2005, 03:45   #2
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There are a number of engine paint systems, any of which will do a good job. As with any surface finishing project preparation is the key. You’ll have to get your engine block clean. (remove hoses, wiring, & etc. prior to any degreasing/cleaning).

Check with a good automotive supplier, and choose cleaning, priming/conversion coating, and paint from a single manufacturer - ensuring compatability. Follow all instructions.

First, lay out plastic sheeting and absorbant pads under the engine, then disassemble and remove everything from the engine (hoses, fuel rails, throttle linkage, wire harnesses, etc). Reassembly will be easier if you mark wires and hoses as you remove them. The more parts you remove before cleaning and painting, the better the finished engine will look.

An engine should ALWAYS be cleaned either cold or very luke warm. NEVER hot.

Don't degrease nor paint rubber engine mount isolator pads.

Good luck,
Gord
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Old 17-11-2005, 14:40   #3
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I was told to clean the part good then sprey OSPHO( I think that is the spelling) on them let them dry a day then paint over top of that. Paint is still holding up.

Good Luck,

Matt
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Old 17-11-2005, 17:30   #4
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“OSPHO” is a good rust converter, comprised of (75%) Phosphoric Acid, Sodium Dichromate, Wetting Agents (Surfactants) and Extenders (pH <2).

Rust converters are solutions or primers designed to be applied directly to a rusty surface to convert residual rust on steel surfaces to harmless and adherent chemical compounds. The most frequently used formulations are based on Phosphoric Acid, which causes the rust to be converted to a firmly adhering, and protective, Iron Phosphate film.

Rust converters can be simply brushed or sprayed on the surface of the metal, after all loose scale, oil, and waxes have been removed. The temperature of the metal should be between 50 & 90oF (10 - 30oC), and (if used outdoors) there should be no risk of rain for 24 hours. Within 20 minutes after application, the converter will turn any rust it touches dark grey or black. The reaction is usually cured after 24 hours, but longer if the ambient humidity exceeds 75% to 80%. The acid will eventually cause hydrogen embrittlement*, so use the minimum etch time that removes all rust.

The iron phosphate coating is not very thick, and not very durable, so some additional protection is still required. Rust converters are formulated to be used as primers, which should always be followed with a compatible topcoat. Unlike traditional coatings, the surface must not be sanded.
As with all acids, use rubber gloves and splash goggles, no matter how weak the solution. When thinning acid, add acid to water. Never add water to acid.
To avoid contaminating the stock solution, never pour used rust converter back into the bottle.

Skyco “OSPHO” is one commercial solution, as are DuPont “QUICK-PREP”, and Sherwin Williams “METAL PREP”. Check the individual product MSDS, noting the constituents, and acidity. The higher the pH, the quicker the acid will etch the metal.

* All acids contribute some hydrogen to the metal structure. This weakens steel by a process called hydrogen embrittlement. I’ve heard it claimed (uncomfirmed) that if you bake the metal at 400F for an hour after acid cleaning, this will drive out the hydrogen and prevent embrittlement.
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Old 18-11-2005, 12:00   #5
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A little nitric acid will get that rust off

JUST KIDDING!!!!!!!!

Even if you use that OSPHO, you'll still want to get as much of the rust off as possible. And like Gord stated, put on a second coat.

I've had real good luck with automotive spray (can) paints.
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