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 Post subject: Re: Painting Frame
PostPosted: April 4, 2019, 5:13 am 
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When restoring rusty parts, I dip them a couple days in a weak acid solution, use fresh water and scrub the parts, then use a propane hand torch to quickly drive off any moisture before either sandblasting, spraying on phosphorus water mix in a universal spray bottle or go straight for rusto’s “heavily rusted metal primer” which can be seen all over my builds. I have not used my oxy/acetylene to remove moisture but a propane hand torch works great and the process can be seen just as Ajmacdon described. I only use acetone (in a refillable sprayer with a Schrader valve on top to pressurize with air) on something I didn’t sand blast and/or dip.

For painting the frame, I’d do a quick wipe down with acetone, wait a half hour to fully evap, then use HRM primer and top with rusto “professional” machine grey. The professional line is worth the price diff. If you need to weld the area again, scratch the area with sand paper to help the arc start immediately then touch up as needed.

You can add hardener to rusto in a can but it is expensive. I would only do that when painting bodywork. To get a really smooth finish with most paints requires a very slow drying mix and a booth to keep bugs and leaves away. A roller wastes more paint and takes longer than spraying but more than makes up for it in equipment cost. I bought a hvlp turbine last year I have not had a chance to try yet. It is a wagner motocoat made for auto finishes. No compressor, dryer, oil separator, air lines, or sep gun to buy. Just plug it in.

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 Post subject: Re: Painting Frame
PostPosted: April 4, 2019, 9:58 am 
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If you have steel that is "pickled and oiled", I imagine your torch would bring some extra oil to the surface, maybe? This is also a more likely material for a farmer to get compared to the really nice cold rolled stuff they sell near SeattleTom.

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 Post subject: Re: Painting Frame
PostPosted: April 14, 2019, 1:12 pm 
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I etched the frame with POR's metal prep, then a two-part urethane primer. Rustoleum over that and 5 yrs/50K miles later still looks great.


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 Post subject: Re: Painting Frame
PostPosted: April 16, 2019, 5:39 pm 
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I haven't done it yet, but am planning on having the frame blasted, then going to etch with POR-15 metal prep, prime with Rust-Oleum primer with thinner and paint with Rust-Oleum incorporating a thinner and hardener.

A question though, I've never painted like this before, any words of wisdom regarding electric gun vs air or gravity feed vs siphon? I'd prefer not to spend hundreds on a gun, but don't want to spend $40 on one that doesn't work either. Thinking about picking this unit up, a 1.4 mm HVLP Gravity Feed Paint Gun from Princess Auto for $65.00.


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 Post subject: Re: Painting Frame
PostPosted: April 16, 2019, 8:47 pm 
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I bought a very similar gun to that and it works pretty decently. I would not go electric - that's for painting your fence.

Anyway, IMO you don't need to etch if you are blasting. I didn't, and anywhere I have had to sand down to weld a tab or whatnot, it's actually been fairly difficult to get down to bare metal. I blasted, then rolled/brushed on POR-15 right out of the can (as recommended) then finished with topcoat out of a rattle can.


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 Post subject: Re: Painting Frame
PostPosted: April 16, 2019, 9:04 pm 
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I bought a similar one from Harbor Freight. It worked pretty well, not that I would know a good one from a bad one. I used it painting my Cushman. I was happy.

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 Post subject: Re: Painting Frame
PostPosted: April 16, 2019, 9:09 pm 
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Thanks Zig and Chuck.

Think HF and Princess Auto stuff is essentially identical, so it's probably the same one.

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 Post subject: Re: Painting Frame
PostPosted: April 20, 2019, 9:19 pm 
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I would only go with HVLP if your compressor is up for the job. I bought a pair of cheap LVLP guns from Amazon a few years back that worked very well. I like the results of the gravity feed better, but you have to be a little more careful about spillage.


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 Post subject: Re: Painting Frame
PostPosted: August 7, 2019, 3:02 pm 
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So I'm hopefully getting my frame sandblasted this week and plan to paint the frame shortly thereafter to avoid flash rusting. I've never painted anything like this before and my painting experience is generally limited to giving something a quick blast with the rattle can. This is what I'm thinking:

-Sandblast frame;
-Use Por15 Metal Prep and immediately etch the metal to prevent flash rusting;
-Wait 15 minutes and use pressure washer to remove metal prep from frame and then set it up in front of a fan/outside in bright sunlight to aid drying;
-Go over with a fine tooth comb and finish welding (any suggestions of welding through the "etch" or should I wire wheel it off?);
-Prime frame with thinned, 3 paint to 1 thinner, grey Tremclad;
-Paint frame with Tremclad using a HVLF gun mixed at 4:2:1 (paint:thinner:hardener) ratio.

I'll probably have to experiment a bit with the thinner and gun, but should the above get me headed in the right direction?

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 Post subject: Re: Painting Frame
PostPosted: August 7, 2019, 6:37 pm 
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Trochu, if you're going through that much effort to get a good paint job on the frame then I'd do any finish welding before starting the shot blast/etch/prime/paint process. My $0.05 worth. Good luck...I'll be interested in seeing the results and hearing your feedback on your method. Bill

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 Post subject: Re: Painting Frame
PostPosted: August 7, 2019, 8:16 pm 
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Still not sure about that etching. I mean, blasting is supposed to be an excellent prep for paint. Also, if you think it will prevent flash rusting, I would suggest testing that theory on a piece of scrap first. I seem to recall some of my etched pieces rusting faster.


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 Post subject: Re: Painting Frame
PostPosted: August 8, 2019, 1:39 pm 
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Blasted metal will still need primer to give something for the paint to adhere to. Etch primer is the best, and I find it easier to spray than build primer too.

Make sure you wear an activated carbon respirator if you use hardener, even the $20 hardware store version will save your lungs.

Practice with your gun on cardboard/etc. There are a few good youtube videos on gun adjustments and what you should get for a spray pattern that will make a world of difference in the quality of the spray job.

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