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Chassis paint type


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Good Evening,

almost ready to paint the frame, prepped by grinding, rust inhibitor, now contemplating rattle cans of tremclad ( rustoleum). Is this going to fail, does one have to use the fancy new (por, etc) products? Appreciate your insights, experiences etc., still a week out from applying. Thanks, this is a great Forum, couldn’t have progressed without it.

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I'm no expert, not even close, but Zero Rust would be my choice.  POR15 is great stuff, but it is extremely brittle.  And, needs  really good prep to bond well.  That's really hard to do on a frame, lots of nooks, crannies, angles etc.  A chip from gravel, dragging on a curb etc, on a place with weak bond allows moisture to enter and start rust.

 

Take a look at Autobodystore.com and search for test on the two. 

 

I guess if I had a completely blasted, impeccably clean frame, I'd go with POR.   With one of my wire wheeled, sanded and cleaned projects, Zero Rust or maybe even Rustoleum as I think they are much more forgiving on prep.

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the same argument is for use of powder coating over paint....powder coating often develops these hairline cracks, heat and cool cycle of the substrate on a humid day/rain/washing....next thing you know the substrate is totally rust while the outer coating prevents your seeing it UNTIL it blisters the coating due to the expansion of ever increasing size of the rust scale.   Nothing lasts forever but you can save your base by routine maintenance on the cover.

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I have heard that you can't buy it any more, but I used Zinc Chromate.  [I understand that it is also what they use on airplanes, and what the military uses (used?) on ships, etc.]

 

I second the deal about powder coating.  I worked in a powder coating operation for several years, and would not use it for anything that is exterior for sure, and I wouldn't chose it for interior, either, although I think it would perform OK in that environment.  (You can't get it to feather out along an edge, if you need to sand it, and it also gums up the sand paper.  I've said this before, but here it is again - I think that it's only advantage in industry is that the parts can be handled & packaged as soon as it cools after coming out of the oven.)

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You don't need the fancy stuff.  Use foam rollers and brushes to apply a good coat of rusty metal red oxide primer.  I like to thin it with mineral spirits and add a splash of enamel hardener.  Once the primer is cured, paint the chassis with satin black tremclad once again thinned with mineral spirits and dashed with enamel hardener.  I have done this on countless projects and you end up with a very durable and inexpensive coating system that lasts a long time and is easy to touch up.  

 

 

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Not sure why people are finding Por15 easy to crack? I have literally hammered on this stuff and hardly even scratched it, little own crack.  I used it on the leaf springs on my Monaco and my old vintage sleds, no cracking and been there for a few years now.

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If I ever get the truck fully mocked up, my frame will be getting the Rusty Metal Primer, followed by automotive epoxy primer and single stage urethane.  I've used POR 15 on a frame once before and didn't care for the final results.  I prefer to spray the Rustoleum  products and have had good ;luck with them although the semigloss black tends to fade out when exposed to UV.

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Look into john deere blitz black chassis paint. It holds up amazing, easy to spray out of a cheap gun, fairly inexpensive. It’s a base/hardener/reducer deal you mix up and spray (or brush I guess?)

 

That said, I went with the nuclear option on my latest build and brushed on oil based primer and enamel for my undercarriage. If it holds up for ten years on a wrought iron fence it’s good enough for my old truck- I’m still going to use automotive paint for the visible body work.

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I like the POR 15, it's very durable, but I do agree the finish when brushed is not the same as a sprayed finish from other products.  I brushed parts of the frame and the floor and the self leveling is great but the finish is not the same as sprayed.  I've never tried spraying POR through a gun.  I did find POR topcoat in an aerosol can and I hit my running boards with it.  It made a nice satin finish, I'll have to see how it wears. The other POR products I've used have been really good and worked as they were intended.  This includes the gas tank system - I just sealed mine and so far it's doing it's job...time will tell.

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If you've already treated the metal with a rust inhibitor then I personally wouldn't spend the $$ on Por15/Chassis Saver. I believe they advise against perfectly clean substrates, I know some people have adhesion problems on clean metal. I used Sherwin Williams Kem on my frame. I've used a rust convertor and then heavy rust primer and top coat on other frames with good results. I mix hardener with the Rustoleum.

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  • 2 weeks later...

I've had good success with sand blasting and spraying on 2 coats of magnet paints chassis saver and then top coating it (within 24 hours) with any good quality paint.  I did a car trailer this way and top coated with rustoleum. 4 Pennsylvania winters later (stored outside) still holding up well.  I did my 47 WFX32 the same way and plan on painting my 55 c series the same way. 

Rob

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On 4/28/2019 at 3:05 PM, NiftyFifty said:

Not sure why people are finding Por15 easy to crack? I have literally hammered on this stuff and hardly even scratched it, little own crack.  I used it on the leaf springs on my Monaco and my old vintage sleds, no cracking and been there for a few years now.

 

I'm not sure either. POR is one of the most durable coatings I've used. I brushed two coats on my frame and underside of the cab, then top coated with rust-oleum flat industrial spray enamel when the second coat was almost dry. I also used this system on the wheel wells and they are still looking good as new after driving it regularly for 7 years... The suspension parts just have two coats of bare POR. They are dirty from use but always clean up nicely and aren't compromised by oil or solvents.

 

With any paint you use, the cleaner the substrate, the better your results. When corners are cut or the prep is flubbed, it always seems that the paint or powder coating gets the blame.

 

With proper prep, one could have an awesome point job with most modern paints available today. An alkyd system such as a red oxide shop primer and top coat, or an epoxy primer and urethane top coat would both provide a durable coating. Alkyds usually have good self-leveling capabilities when brushed. I don't mind a couple brush strokes, drips, or sags on a frame either.

Benjamin Moore makes some nice alkyds in their "Super Spec" line. Also their "Corotech" line has alkyd shop primer and Alkyd Urethane enamel for a step up. You can add hardeners for increased durability.

 

Even a water based DTM such as rust oleum sierra performance would be good.

 

Eastwood and Bill Hirsch also have  some good chassis paint systems that are said to produce excellent results. Some folks even prefer the Hirsch product that's comparable to POR over POR itself. Eastwood also offers an internal frame coating system that is rattle can based but deployed from a nozzle on the end of a long tube.

 

I don't believe that powder coating is necessarily prone to cracks and hiding rust (especially to the point when there's no metal left and only rust!), nor unfit for exterior use. Personally, I wouldn't use it for coating a frame, but for smaller parts, wheels, or bumpers, it would be a great system. Once again, it's all in the prep. If you powder coat a rusty surface, the rust will come back eventually.

 

A key point is, any of the above coatings are light years ahead of what was applied at the factory. Don't forget your mask and gloves.

 

 

Edited by John-T-53
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The POR15 on FEF is still rock solid looking like the day I painted his frame and suspension parts.  Powder coat IMO is more prone to cracking, as I observed it in a previous job every day.

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On 5/14/2019 at 6:26 AM, ggdad1951 said:

The POR15 on FEF is still rock solid looking like the day I painted his frame and suspension parts.  Powder coat IMO is more prone to cracking, as I observed it in a previous job every day.

 

My car hauler was powder coated from factory, 6 years later it is coming off in huge chunks, once a rust bubble started it just spread all underneath the coating. Just scraped or brushed off what I could and Por15 the main spots and black undercoated the rest. Powder coating is great, but still not much better in salty conditions 

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I think the amount of prep and type of paint is directly related to our local weather and roads.

Since my vehicles never or at least very seldom encounter road salt corrosion resistance is less of a concern for me.  If they do get some salt exposure a through bottom wash is in the cards soon.  Local carwash has one of those in the automatic stall.

 

Also, they never see gravel roads, so chip resistance isn't an issue either.

 

good cleaning, wire brush, maybe a little blasting if I find deep rust, then a coat, or several, of rustoleum-type paint and I'm good to go.

 

But, good coverage is mandatory.  I usually spray everything, but on an undercarriage a brush can help push it into crevices.

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The thing with powder coating I've noticed is it's inability to get into the tight and hidden spots. Like what happened to NiftyFifty's trailer, on fabricated assemblies like frames or trailers there will likely be a small gap in the coating where water can enter into the spaces between members. Corrosion starts there and works outward...bubbling up the coating as it moves.

With paint, it usually flows into these spaces by capillary action and makes a good seal....most of the time.

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31 minutes ago, John-T-53 said:

The thing with powder coating I've noticed is it's inability to get into the tight and hidden spots. Like what happened to NiftyFifty's trailer, on fabricated assemblies like frames or trailers there will likely be a small gap in the coating where water can enter into the spaces between members. Corrosion starts there and works outward...bubbling up the coating as it moves.

With paint, it usually flows into these spaces by capillary action and makes a good seal....most of the time.

Good point.  In areas like bolted or riveted crossmember to rail connections, there will be a little movement.  tiny, but movement, as the vehicle crosses uneven roads, especially at an angle to the direction of travel.

Hard, brittle coatings don't tolerate that well and crack at the joint.

John Deere has some issues a few years ago with that.  High dollar mowers/garden tractors with powder coat coming off in sheets.

Edited by kencombs
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58 minutes ago, John-T-53 said:

The thing with powder coating I've noticed is it's inability to get into the tight and hidden spots. Like what happened to NiftyFifty's trailer, on fabricated assemblies like frames or trailers there will likely be a small gap in the coating where water can enter into the spaces between members. Corrosion starts there and works outward...bubbling up the coating as it moves.

With paint, it usually flows into these spaces by capillary action and makes a good seal....most of the time.

This is one of the main weaknesses of powder coating - it's very difficult to get good coverage in corners & crevices.  This is also a problem in electro-plating, but in that situation, we would up the amps right at the beginning to get into the corners, then back it off so we didn't "burn" the main surfaces.  (We sometimes also would use a probe type anode to reach into larger openings.) 

 

As another has stated, I agree that a brush is sometimes the best option.  Maybe do the first coat with a brush, then spray over that.  That gets you the best of both worlds.  I've seen some brush-painted vehicles from years ago, and it was an art just like spraying.  (Using a really good quality brush that doesn't shed bristles, and a slow thinner, for instance.)

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This is my frame - two coats o' POR with either one or two coats of Rust-Oleum industrial flat black on top. You can see some minor runs on the outside of the rail on the side shot, but this is the only time they're noticed....

IMG_8945.JPG

IMG_8941.JPG

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