Acetone vs Wax & Grease remover before epoxy

When reading about surface prep for epoxy I keep hearing 80 grit and acetone is recommended. But if you read about surface prep in the auto forums, wax and grease remover is suggested. It's said acetone, mineral spirits and lacquer thinners have to many contaminants.. But many of the wax and grease removers are water based, and I cant wrap my head around a water base cleaner better than a solvent.

What is the best surface prep cleaner for marine epoxy to steel?

Thanks

 

Auto forums ? I'd guess car wax needs to be thoroughly removed before car repaints, but where is the wax on a steel boat ? Acetone flashes off so quickly, I doubt it would be as effective or easy to use as other agents.

 

Acetone evaporates so quickly it's hard get all the contaminates removed from the surface, but it does move them around nicely. On a small surface it can work, on large areas this makes it difficult to use. Products for surface prep tend to evaporate a little slower so you have time to remove them and the gunk from the surface.

 

A well known paint manufacturer (Dulux) always specified to degrease metal surfaces with mineral turpentine, prior to painting, probably with "mill oil" in mind, used in the rolling of sheet metal products, if that advice was appropriate for one-pack coatings, I'm not sure that epoxy would be in need of a different approach.

 

Epoxy surfaces shouldn't be cleaned with solvents before application of subsequent coats of anything. The appropriate approuch is to wash the surfaces with a slightly alkaline (soap) rinse. Next the surface is "toothed" to an appropriate grit and finally "tacked off" to remove dust and other surface contaminants, left from the teething process. The washing and toothing process can be combined if desired, using proper procedures. A common method is, to use a ScotchBrite pad to tooth up the surface as you wash it down, killing two birds with one stone.

Slower evaporating solvents, such as spirits or mill oil on metals isn't to clean the surface as much as to slow the oxidation rate, before protective coatings can be applied. Single part polyurethanes are compatible with these solvents, so not a contamination issue. Acetone flashes too fast as mentioned, for contaminates to be removed, usually just smearing it around and leaving a haze instead.

 

Does "turps" leave a residue that contaminates the surface ? I don't know, but here is a product blurb that claims not to leave any residue:

APPLICATION
Thinning Oil-Based Paint
• To achieve optimum results always follow paint manufacturer’s
directions when thinning paint.
Removing Waxes and Polishes
• Always test on a small area first. Use direct from the bottle. Saturate a
lint free cloth with Diggers Low Odour Turps and wipe in one direction
to remove containments from surface. Use a clean part of the cloth for
each wipe. For vertical surfaces start at the top and work downwards.
Cleaning Paint Brushes
• Place brush in jar with Low Odour Turps, squeeze out paint and
rinse with strong soapy water.
Degreaser
• Use undiluted to remove built-up oil and grime without leaving any
residue.

 

"Diggers Low Odour Turps" is nothing more than mineral spirits (naphtha). Most mixtures of mineral spirits (three basic types) will leave an oily residue on non-porous surfaces. Find out for sure and pour a few drops on a piece of glass (the clear window kind) and let it dry. This is likely the most used solvent in industry and does lots of good stuff. In the metal prep industry, they'll use mineral spirits as a cleaner and short term oxide preventor and when they're ready to apply finish the residue is removed with an alcohol rinse, which does evaporate cleanly. Acetone is often used as sterilizer in the medical industry, though a lot more costly than alcohol. Again, with most polyurethanes and alkyd paints, not an issue, because these also have naphia derivatives in them, but with acrylics and some two parts, you run the risk of fish eyes. The quick way to find out which will cause issues with mineral spirits is to read the MSDS, looking for "petroleum distillates". I find I use toluene and xylene much more often as cleaners, than mineral spirits, because they are faster drying and "drier" than the naphthas. Technically mineral spirits and naphtha are a bit different, in that naptha is slightly faster and drier than spirits, but they both come off the "tower" near the same temperature. In contrast toluene and xylene come off the cracking tower at higher temperatures, which is why they cost more and evaporate faster (okay this has more to do with molecular weight, but now it's too technical).

 

OK, so you are saying that he should use a two-step process, first the "turps" or similar, followed by the "metho" (ethyl alcohol + methyl 5% or thereabouts) ? Don't you hate the way these items have different names in different parts of the world ! That sounds easy. I will get around to doing that glass test with various solvents, one called "shellite" here, sometimes "white spirit" when is basically like gasoline ( petrol !) and clear, both in colour and of any additives, it will run a car engine if you run out, seems to leave no residue that I have noticed, but we shall test it.

 

Thanks.. Here's what Ive gathered..

The single stage coatings are compatible with spirits because they use spirits as the solvent..

The two stage epoxy primers require specialized brand specific wax and grease removers because they don't use solvents..

So that would put my marinepoxy in the two stage category requiring a wax and grease remover. Would I be fine with any wax and grease remover from the auto parts store before applying marinepoxy to steel?

 

There are two general types of degreasers, and I am using that term loosely
Diluents dilute a liquid. Is like adding water to a latex paint. As water base paints base is water, the addition of water merely makes the solution less viscous
Solvents on the other hand can change the chemical structure of what you add it to and the residue can can become non oily by this decomposition.

An example of a diluent would be a varsol based paint thinner for oil base paints. Varsol by itself will leave an oily film.
Lacquer thinner, trichloroethane III ie Brakekleen are , I suspect acetone as well, are solvents that will destroy the residual film of light oils on metallic surfaces

Ignoring health risks, breathing these items, a solvent is what you need.

Interlux 202, is used as a prewash for steel and aluminum prior to painting

Certainly your epoxy supplier will have a recommended pre wash product to remove any oily residue.

Most important is that you need to remove the mill scale from hot rolled steel. If done by sandblasting, this will roughen the surface enough for additional paint bonding.

If not, you could sand the surface with 60 grit paper for aluminum or 80 grit for steel,prior to painting.

The mill scale MUST be removed! All of it and sandblasting is the best way.

 

Thanks for that Barry.

My supplier said acetone, and Id probably be fine using that followed by denatured alcohol (both on hand) as long as the metal is clean and rough.