Metal paint

[over40pirate]

This could be a fish story.
I met a guy who had his steel propane tank hanging off the back of his boat as many cruisers do. It wasn't rusted. My steel tanks were lasting less than 2 years of cruising on salt water.
I asked him about it, and he told me he sanded them down good, them primed with a primer that had fish oil in it. He said it was hard to find anymore.
Sounds fishy, huh.

[Charlie]

Originally Posted by over40pirate

This could be a fish story.
I met a guy who had his steel propane tank hanging off the back of his boat as many cruisers do. It wasn't rusted. My steel tanks were lasting less than 2 years of cruising on salt water.
I asked him about it, and he told me he sanded them down good, them primed with a primer that had fish oil in it. He said it was hard to find anymore.
Sounds fishy, huh.

Could be something to it. I've never seen a rusty fish before.

[Alan Wheeler]

I guess I'll go with the two coats of zinc primer and then a two part epoxy paint.

No, single pack Epoxy. I stated single pack for a reason. Two pack will have a solvent that will react with the primer/undercoat.

[David M]

Charlie...epoxy will not bond to single part paints...not very well at least. So painting epoxy over a single part zinc primer might not be the best idea. I would strip off all the rust and bring it down to brite metal and then put a few coats of a tough epoxy like Interlux 3000...and then put whatever finish coat you want over the epoxy. The trick is to not ding the paint which of course will start blisters under any kind of coating....including zinc chromate. There are zinc chromate epoxies out there...Google it.

[hellosailor]

Wheels, why do you say 2-part epoxy has a solvent? By definition, epoxies DO NOT have a solvent, they cure by chemical reaction not solvent kick-off. Which leaves the "one part" epoxies as something I've always wondered about--if there's no two parts, maybe they use a solvent? And aren't really epoxies?

[Wotname]

Hello,
I am no paint chemist but I have an "internet value" opinion. I wondered about the single pack epoxies also and the best I could come up after phoning a couple of paint companies is that they cure by moisture (humindity etc). The ones I am familiar with are best described as epoxy modified enamel, rather a loose term I know and sounds more like a marketing term doesn't it.
The particular one I have used a fair bit (say 20 litres) certainly has a harder surface and higher gloss yet seems as flexible as a run of the mill alkyd paint.
I guess epoxies are a generic term these days as some epoxies do have solvents IIRC and others are water soluble until cured.

Seemed strange the first time I used a water soluble 2 pack epoxy and washed the brush just in water

[Alan Wheeler]

Wheels, why do you say 2-part epoxy has a solvent

Yep good question. Yes epoxy paint does have a solvent. The reason for this is that epoxy paint is not epoxy resin as such. Paint has many other additives. There are the fillers and binders for a start. They would be the biggest part of the additive package. Then there are thoxotropic additives. That is what keep the paint on the surface you just painted on. Some paints will have extra's like pigments and maybe even powdered metals for impact hardness. And then there are the products that create "flow" so as the brush lines and bubbles settle out to a smooth surface. So the result is a very thick gunk that would be impossible to get onto the surface. The solvent is there for two reasons. One important one is to get it from the can to the surface. The other is to keep certain components apart. This is especially important for paints like single pot epoxies. These paints have both components in the mix. They bind together when the solvent evaporates and thus harden. Depending on the type of paint, different solvents are used. There are single pot epoxies that are water based and oil based. But all two pot epoxies that I know of use solvents that will eat an oil based product and create a reaction.
I hope that helps.

[GordMay]

As Wheels indicates, solvents* are the liquids in paints, that suspends the pigment and resins, and transports (reduce viscosity) them from the paint brush to the surface. The solvent then evaporates and leaves the paint film behind. Generally, the less solvent in the paint, the higher the quality, the lower the VOCs, and the better the coverage.

* Acetone, lacquer thinner, and denatured alcohol are common solvents used with epoxy products.
Water, as used in water dispersible epoxy, is also a solvent.

[David M]

The paint Petit sells that they call MonoPoxy is not an epoxy at all. Epoxies only cure through heat and a chemical reaction. They do not cure through evaporation. The litmus test: put acetone on something you think is an epoxy...if it dissolves it is NOT an epoxy. It could be a two part LPU but it clearly is not an epoxy.

[hellosailor]

I was told the old Rustoleum had fish oil in it. Why not? Whale oil was used before kerosene in lamps, right?

[Wotname]

Product could have been Fisholene (or similar). Paint with with fish oil in it, smells like sardines gone off. Still available in Oz (and maybe NZ). Was very popular 30 years back for "rustproofing" cars used on the beach. Paint & Resins, Fisholene - Browse catalogue or add product to Cart.