Painting Question

A previous post of mine brings up the question, to prime or not to prime. Myself I have never primed anything that I have painted. Working on mainly 30, 70 and 90 series tractors I have noticed CASE never used primer either, but that does not mean it is the correct thing to do. I know little about painting and different products and have only used CASE supplied enamels. A paint supplier once told me you prime bare metal if there is a chance surface rusting could occur before finish painting or prime with a sandable primer if there are small imperfections you would like to remove. Your thoughts gentlemen? Rod.

I like to prime, it adheres much better than paint. Also bare metal is harder to cover with paint. Or at least take a few more coats then have a risk of having runs in it if not patient. Also if you're real particular in your body work. You can use a filler primer to finish out small dents and sand it down! My 2 cents

I agree with the other poster, always prime. Even when using a rattle can I prime first. Covers better and adheres better. Always use a dark color primer under a dark paint and light primer under light color paint. Takes less paint and gives more depth to paint job. My son is a professional auto painter, and he never paints on bare surfaces. Primer is cheap insurance compared to the cost of paint.

Rod,

another thing to considers is phosphatizing wash or etching primer. modern oems often use a phosphatizing wash which cleans and etches the metal to allow the primer to adhere better to the substrate (metal). an etching primer does the same. Helps guarantee the bond so you paint won't peel off like a decal.

Always primer on bare metal. Sometimes even a sealer over that. I have painted cast with well adhered paint with paint only on a few work tractors and it held ok.

They may use an acid etching primer in the paint color. That's what I use even on trailers. Most folks only think of primer as being red or grey oxide, but I would be surprised if a manufacturer used that.

I would agree that primer on bare steel is a good idea for additional corrosion control but is used frequently to block out irregularities in the bondo and feather edged chips in existing paint it comes at a cost in additional labor of block sanding it after application to remove the tale tale waves and remaining scratch's that are a dead give away it has been repaired. For that matter any repair job done by a pro if done correctly should not be distinguishable from the rest of the straight metal surrounding the damaged area. That is to say you should not be able to tell it was fixed,You see a good repair job is dependent on preparation and if done properly you can obtain a showroom finish. Let me add that steel used on aircraft is etched and primed with the exception of some areas of titanium that is frequently used in extreme high heat areas like engine thrust reversers they are not painted. Aircraft are painted with polyurethane enamel.You may not be looking for show room quality I know I'm not because I use my tractor. Now as far as painting over bare steel weather it is sanded or blasted it really should not be an Issue it will stick and it sure is better than no paint at all.. I don't know if anyone has used the polyurethane enamel on their tractor It is a great product that leaves a shine similar to a compounded lacquer job really nice. I have even in the case of high metallic paints that in the 70s were not good with polyurethane because of there long dry time the heaver metallic content would run together making a mess of the job, almost as bad as a large mosquito landing on the hood. I have shot acrylic lacquer as a base coat and a clear polyurethane enamel as a finish coat. This was pretty common in the 70s with the painting of murals on vans. This is just my opinion.

Hey Rod, I did not mean to stir the pot. I have pitting in my dash and hood, so I etched with muriatic acid and I will have to fill lightly with a light skim of that green filler then sand. I really appreciate you rolling on with an additional post. Thanks Chuck

Your primer needs to match your paint system. Some paints can be sprayed directly onto bare metal with very good results, and some need a particular primer to last well.
Most farm equipment from the late 30's to the mid-seventies was painted with Alkyd Enamel. This paint sticks to almost anything, but is soft and fades badly. Also, manufacturers were not too worried about a perfect finish. They were more worried about low production cost and preventing corrosion. Also, they were not painting badly corroded metal.
Modern paints are much harder and more fade resistant. Also, high-end epoxy paints require specific primers and specific time intervals between different coats. The trend has been for newer paints to become more expensive, more dangerous to apply, to require a more complicated application procedure, to require much better surface preparation, and to be more demanding with regard to the proper ambient conditions at the time of application. In exchange, the final result is much more durable, requires less maintenance, and is much more fade resistant.

My favorite primer for most types of enamels is John Deere Buff Primer-sealer. I use it all the time. It works well under flambeau red, LC gray, Case red, etc.

(quoted from post at 13:11:08 03/09/15) Always primer on bare metal. Sometimes even a sealer over that. I have painted cast with well adhered paint with paint only on a few work tractors and it held ok.

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Im in a similar situation, do I need to sandblast my engine and frame even if the original paint is adhered good or could I just pressure wash it really good and paint over it?