General paint advice - epoxy vs enamel + primer?

[wortgames]

Hi all, I'm rebuilding a machinery trailer and wondering on the difference between these two approaches?

I've used off-the-shelf epoxy metal paint before (eg rust guard / hammerite) with good results.

My local industrial supplier reckons the proper way to do it is to use a zinc phosphate primer then an enamel paint, possibly with hardener added. He can't really give me a reason, just that's the way the structural / machinery guys do it.

I have little experience with spraying, but I'm tempted to get myself a spray gun for this job.

Any opinions?

 

[piman]

Hello Wortgames,

if the Hammerite you use is the same as we use, it is not a particularly good choice (Nor is it an epoxy paint). It had a good reputation once but the original makers were taken over and the current product is very average.

I would use a proper epoxy primer then overcoat with enamel.

Spraying will be quicker but obviously you'll need to practice and get some guidance on gun set up.

Alec

 

[wortgames]

Hi Alec, thanks.

Being an ex-pat I've always just called it 'Hammerite', but it is sold under a couple of different brands here. Probably the easiest to find in hardware stores is 'White Knight', they have an 'epoxy enamel' and a 'hammered finish' with virtually identical labels and instructions, so I figured it was all basically epoxy paint, just with or without a hammered finish. Is that not true? I've only used the hammered version so far, but it sticks like glue to bare metal and light rust and goes very hard.

Either way, I guess I'm trying to understand what advantage I'll actually get from adding a second product and process. I already know the single-stage product works well and is quite forgiving of imperfectly-prepared surfaces, so what am I missing?

(BTW I'm leaning towards a flat white finish - I know the 'primerless' epoxy enamel is readily available in the local hardware store in 4L tins and also aerosol cans for touching-up, but I'll be starting from scratch with primers and topcoats, so I want someone to convince me of the advantages!)

 

[richie00boy]

If it is a single component product and air drying, then it cannot be a true epoxy. Also, epoxy is usually not great in conditions exposed to sunlight.

Epoxy primer and 2 pack topcoat will be the best performing, and will be fine brushed as long as you stick to the recoat window.

The all-in-one paints tend to stick better to slightly rusty metal and can chip easily on new metal. So in your case you still need to prime really.

 

[wortgames]

Thanks richie.

Another issue (that I'm fast realising could be significant) is that there is no way in hell I'm going to be able to get this thing back to virgin steel all over - the best I'm going to achieve in the real world is a good blast with a wire wheel on an angle grinder, followed by a wipe down with a turpsy rag immediately prior to painting. This will almost certainly leave some pits and surface rust in the original steelwork. Plus I'm working outdoors (and it's winter here, so we're getting a bit of rain). The new steel is blue primed, but obviously the exposed parts and welds are already oxidising.

I've decided on white as the final colour BTW.

Does any of this sway the recommendation? Is epoxy primer as good over light rust and pitted steel as the single-stage product I'm used to?

 

[langy]

Yes 2k Epoxy will do the job, you shouldn't wipe down with a "turpsy " rag either or a thinners rag, use panel wipe