Re: [Chrysler300] Powder Coat rams

["DeBusk Thomas L." <tleed@xxxxxxxx>]

I finally found something I know enough about to comment on!

I have a cheap but effective home powder coating gun and have done enough parts & research to have learned the following:

One common misconception regarding powder coating is that it's all the same chemical composition. But just as there are many different kinds of liquid paints (oil-based, enamels, urethanes, polyurethanes, etc.) so in powder coating there are many different chemical compositions. Some are polyester, epoxy, hybrid (some combo of polyester & epoxy), etc. Each different kind has it's own chemical properties. Some cure at lower or higher temperatures and/or withstand heat better. Some will withstand exposure to gasoline while others will quickly deteriorate. Some are very vulnerable to degradation by UV exposure, while others are not. If you just go ask somebody to powder coat your car parts, it's no telling what you'll get, unless you ask specifically for a particular kind of coating. I have a couple of high temp coatings I use on manifolds, but I wouldn't use them on parts exposed to the sun. Similarly, parts on the undercarriage might be fine for UV-sensitive coatings that are more resistant to chipping or oil & gas exposure. Incidentally, toughness & resistance to chipping is frequently touted as a benefit of powder coating, but that's really a function of the chemical composition as well. Some are more hardy than others. And it's really a poor assumption to think that just because it's a car part, the coater should know what kind of coating is best to put on it. You might coat a car differently that's going to be garaged the rest of it's life versus one that's going to be outdoors. Why would you assume the coater will know how much you intend to expose a particular part to heat or chemicals like gas, oil, and brake fluid?

Like liquid paints, powder coating can be applied in various thicknesses. You can block off or cover sensitive threads or holes that have to maintain their dimensions. But that's prep work and you'd need to discuss that with you're coater if you're not doing it yourself to see whether they can protect the dimensions efficiently & effectively or not. If you did it yourself you might be able to be a little more careful than somebody trying to get a lot done in a hurry. As with liquid coating, the importance of good prep work can't be over-estimated.

As for removal, I've never met a powder coating that doesn't remove with the traditional methods, i.e., with chemical paint remover, sand-blasting, or scraping & sanding. Of course, that doesn't mean they don't exist. See above. Again, it's a function of the chemical composition. Powder coating more accurately describes the application method, NOT the chemical properties of the coating you're applying. Some kinds of powder coating might be more resistant to a particular removal method than others. But many of even the toughest ones will remove with a good paint stripper.

Powder coating hates impurities on the pre-coated surface. As it's baked on, it forms a liquid shell, which will bubble quite enthusiastically if there's something underneath that will convert to a gas at baking temperature. Ask me how I know. So your parts have to be scrupulously clean. That can be really hard to accomplish with parts that are porous or have hidden crevices filled with decades of grease. I've even incorporated my own fingerprints into translucent coatings. I guess that's one way to personalize your ride!

I once tried to powder coat a whole engine block. Didn't work, but not for a reason I expected. I used a massive oven large enough to contain the whole block The coating I was using was supposed to be held at 400° for 20 minutes after the powder flowed as a liquid. That part worked fine. But the block didn't cool down right after the 20 minutes were up. The thermal mass was enough that it kept on baking the coating until it destroyed the integrity of it. I didn't have the wherewithal to experiment around until I discovered just the right balance of heat and post-baking cooling.

On the other hand, I've since discovered that some urethane car body paints make great under hood paints even for engine blocks and are a lot easier to apply. Powder coating isn't an ultimate fix-all solution. Powder coating is a great "weapon" in the arsenal of the savvy restorer, but, like many things, it pays if you learn to wield it with a little wisdom & knowledge.

Thomas DeBusk




On Jan 30, 2013, at 5:22 PM, Keith Boonstra <kboonstra@xxxxxxxxxxxx> wrote:

> Out here in West Michigan we make a huge amount of office furniture, and 
> powder coating is about the only way they finish the product anymore. 
> It's a non-toxic and non-polluting process, and actually fairly 
> economical and good looking. The air quality folks love it. It works by 
> inducing an electrostatic attraction between the surface to be painted 
> and these tiny little bits of dried thermoset plastic or polymer in a 
> powder form sprayed at the part. Then when you heat it to about 390 
> degrees it melts and flows onto the surface. Works great, but this is 
> indoor furniture.
> 
> The problem with using powder coating for anything that will get wet or 
> damp from time to time, is that powder coat is almost never as complete 
> as an applied liquid coat of finish, and the inferiority can show up 
> quite soon after application. When the powder is sprayed onto the part 
> it's almost impossible to get the powder to wander into all the little 
> corners and crevices, and there will be only a thin coat, if any, in 
> those spots. Then over time rust begins at those thinly finished 
> corners and proceeds to undermine the powder coat starting at that 
> point, and it starts flaking it off. Then about the only thing to do is 
> put your part back in a burn-off oven at 800+ degrees to remove what's 
> left of the coating and start all over.
> 
> On the other hand, when you spray wet coats of any finish on the part, 
> the wet material actually flows into all the corners and crevices, and 
> gives you the most complete coverage possible short of dipping the 
> part. You can use enamels to paint an engine as they did at the factory 
> and get a nice result, or by using a base/clear urethane (2K) you'll 
> have it looking like new for tens of thousands of miles. Either way the 
> liquid coat performance will always be far superior to a powder applied 
> coat for endurance. The only downside is that it's just nastier to 
> apply it wet.
> 
> And for those of us with the silver hemis, one added advantage of using 
> a liquid 2K finish is that you can tightly control the exact amount of 
> gloss you end up with by adding flatting agent to the clearcoat. Gloss 
> is next to impossible to control with the powder coat method.
> 
> One final option to note is good old baked enamel. Most enamels can be 
> baked while they're still wet at 250-300 degrees, and give you a really 
> tough finish quickly. Better drag your wife's oven out into the garage 
> before you use this technique though.
> 
> Keith Boonstra
> 
> On 1/30/2013 2:45 PM, Ryan Hill wrote:
> > I had this discussion with John Hertog about 10 years ago when I found he was powder coating an engine and wondered why. After some debate, he eventually agreed with me that powder coating wasn't really a great choice for engines, especially when performing a real restoration. (Perhaps he agreed just to end the discussion.....) In my opinion, powder coating looks great and is a fantastic coating for many things; engines are not one of those things, if you want it to look like it should. For less money and greater ease you can paint an engine yourself with good quality primers and paints and get a much more authentic, long lasting finish.
> > Just my two cents.
> >
> > Ryan Hill In rainy (as usual) Vancouver, B.C.
> >
> > To: Chrysler300@xxxxxxxxxxxxxxx
> > From: rpjasin@xxxxxxxxxxx
> > Date: Wed, 30 Jan 2013 10:10:07 -0800
> > Subject: [Chrysler300] Powder Coat rams
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> > I've got to chime in on the engine powder coat question as well, if I might.
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> > In 1985, I had my rams and valve covers powder coated on my 300G. Now the
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> > valve covers are black and the rams are red, so it is a bit different
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> > situation than the 300K. I've never had a problem with the black parts,
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> > they have held up well.
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> > The red rams though, turned a lighter, almost pinkish color after about 10+
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> > years. Why? I really don't know, the black stayed black, but the red
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> > didn't. My point is that powder coating is not necessarily the absolute
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> > best way to go in every situation, as many people believe. For one thing,
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> > it is very difficult to remove if the need arises. Abrasive blasting is
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> > about the only way to get it off, and you must use an aggressive media to do
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> > it. Any screw thread hole that get coated must be rethreaded with a tap or
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> > die to get the threads into spec again.
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> > In building on Mike's point, if the engine block will be painted
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> > conventionally, and the rams and valve covers powder coated, you may find
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> > yourself with a mismatch at some point in the future you had not
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> > Having said that, you can always paint over the powder coat with
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> > conventional engine paints, that's what I did on my rams, by hand mind you,
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> > with an artists' brush, and they came out looking great, but an engine block
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> > repaint would be more difficult.
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> > Bob J
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> > Hi Larry,
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> > You probably already know this but I wasn't sure by the way your message
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> > reads; The entire engine is turquoise, not just the rams and valve covers.
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> > Also, why powder coat? Harder to touch up if needed and you still need to
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> > match spray able color for the rest. I can probably find the formula I mixed
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> > to closely resemble the old plasticoat #210 turquoise which Gil said was a
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> > good match.
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> > A single stage urethane applied over either epoxy or self-etch primer is
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> > very durable.
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> > Mike Laiserin
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> 



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