Question for metallurgists, chemists, or maybe painters....

[tkent02]

Painting my motorcycle trailer, because it far too ugly even for dirt bikes. Rattle canning it, with not even a whole lot of prep, just knocking the mud and sand off and shooting. Using the stuff like Rustoleum and Hammerite that say they work OK over rust... I know that's not really true, but I don't really care how flawless it looks.
Easy is good here.

Some of the spray paint cans say not to use them on galvanized metals. Why?
Does it make poisonous gasses, the paint won't stick, maybe it eats away the metal? Maybe the finish ends up looking funny? Maybe the paint looks like crap? Maybe something serious will happen, the Earth tilts off of it's axis or something?

About half of the trailer is galvanized, the half I haven't painted yet.

[GSCafe]

I suck at painting, so what you're doing sounds just great to me.

[tkent02]

I'm getting pretty good at it, but a 1961 Rocket trailer just isn't going to get the time and effort one of my two wheeled masterpieces gets.


Before pic...

[Fjbj40]

Generally, with galvanized metal, paint has a hard time adhering. That's why galvanized metal is typically left unpainted. No it does not make poisonous gas, it just does not stick well.

[tkent02]

Generally, with galvanized metal, paint has a hard time adhering. That's why galvanized metal is typically left unpainted. No it does not make poisonous gas, it just does not stick well.

OK, thanks. Is a can that does not say not to use it going to stick any better? Or does it all suck? Can I use a special primer or something?

[metalfab]

OK, thanks. Is a can that does not say not to use it going to stick any better? Or does it all suck? Can I use a special primer or something?

Agreed it is an adhesion problem, it is hard to get paint to stick to galvanized. Sand it with 320 paper for the best paint adhesion without scratches. Galvanized steel does put off poison gas if you weld it.

[GS1150Pilot]

Plasti-Dip it.

[tkent02]

Plasti-Dip it.

Will that work any better?

[GS1150Pilot]

It should stick, especially on older galvanized surfaces.

[tkent02]

It should stick, especially on older galvanized surfaces.

The part I have left to paint are the tracks the bikes roll up. Is the plasti-dip tough enough for the tires to roll on?

[jbird7262]

Why not use some of the rattle can bed liner stuff, probably a bit thicker and more durable, just hit the inside of the runners with a wire brush, tape off the outside u don't want painted. Walmart has it.

[GateKeeper]

The part I have left to paint are the tracks the bikes roll up. Is the plasti-dip tough enough for the tires to roll on?

Probably not....

Plastidip is best on parts that have a no contact, if you rub an area too much and too long the plastidip will come off

[bonanzadave]

Will that work any better?

Hit it with some Bulldog first.

[Gorminrider]

Bad idea putting enamels on galvanized surfaces. ...."my theory which is mine" (if you remember Monty Python) developed in saltwater environments: zinc coating is sacrificed electrically to protect the steel , so paint even successfully applied puts the corrosion protection to any breakage in the paint surface , where before, the whole surface of galvanising somewhat protected the worn off bits, now you have pustules of powdered zinc at any break or edge lifting the paint off
otherwise
Google is your friend but here's one if you believe it.

https://diynovice.wordpress.com/2009/09/16/spray-painting-galvanized-metal/

[Gorminrider]

...I'd be trying som galvanising spray-on instead. Reports I have say it works ok though nothing beats a proper dip of the metal