Power Coating

E

El Toro

Member
Hi All just like to know what you guys think about Power Coating.........................the good and the bad? I will voice my feelings later. I know its popular to use on frames and a lot of manufactures use the process. Thanks
 
Im a novice, but I do have an opinion. I think powdercoating is spending a lot of money on a product that is very durable and will outlast a lot of other products. The down side would be maintainance and re-spotting any areas that need touch up or repair. Personally, I think the SPI Epxoy would be an excellent choice if you want a satin black. Three coats should be awesome. Its easy to touch up.
 
On one item I produce, commercial awnings with aluminum frames, if the customer wants the frames a color (they are mostly left in raw aluminum), powder coating usually costs approximately 1/3 of what prep, primer and SS urethane wet coating would be.
It appears to be popular for a variety of manufactured metal products due to ease of use, environmental concerns, and overall cost.
That all said the top shelf finish I offer if cost is no concern on outdoor metal fabrications is quality urethane on SPI epoxy primer.
 
One downside to powdercoating is if an item needs bodywork . A high temp epoxy can be used, but you pretty much need to blocksand & recoat to have a perfect surface, paying for it twice. Learned that on bumpers. Also not as durable as I thought it would be.
 
I feel the same as you jlcustomz.............my two car trailers 4 years old the are a rusted mess both were power coated. My brothers trailer was a factory painted trailer 6 years old looks great. Also some of the other projects just don't seam to hold up and when chiped go right to rust and then creeps under the coating. Reminds me of por-15. Looks very nice when new. Hell I painted a rusty metal metal brace for oudoor use with SPI epoxy and acrylic enamel a few years ago and still looks great even when I bent a section.
Just my opinion
 
I powdercoat industrial parts for a living. Yes, both products have their cost and durability issues. Bottom line, is the majority of powdercoat is epoxy, so you get the same issues as spraying epoxy as far as the product powdering with uv exposure. Those are the two or three dollar a pound powders most places use. Move up to hybrid which is part epoxy part polyurethane and powder costs go up, go to full out polyurethane and its 2-3 times the price.

Powder is cheaper because you dont really need spray paint talent to apply it, but the only thing that makes it durable is properly baking the parts. Big trailers and frames take a long time to get up to the 400 degrees it takes to cure most powders, and that has to be maintained for 10 minutes once it gets to that temperature. Otherwise you have no adhesion and it chips easily. So choosing a powdercoater, you can give a rats ass of how pretty his booth is, how digital state of the art his guns are, you choose the guy with the kick ass oven.

We only have an 8 foot oven, so even powdercoating the subframe for the Camaro gave us issues with curing. We are going to try a PPG 300 series polyurethane on the chassis for the 36 since its far too long to bake properly. It was 60 bucks a gallon and 35 for the activator quart for a 7:1 mix. They make it in different colors from regular ppg stores, but most have to order it in so it takes a few days.
 
its like any other coating.....durability and how long it lasts is all in how well its prepped and applied. do a crappy prep job and apply paint, it aint gonna last too long. powder is no different. if a part is blasted perfectly clean and the powder is applied and cured right then it will last a long time. i personally dont have too many things powder coated. only things that would be difficult to spray. something where the part would have alot of shadowed areas where i cant get spray into. on bikes i prefer powder for things like foot beg and anything your feet go on. its just a thicker coating and has more mils so it takes longer to wear through it when its constantly being stepped on.
 
Last I checked into powdercoatings, Cerakote seems to be replacing a lot of other brands at shops near me. They also have a 1 part thin clearcoat (mc160) which is air dry & gets use on polished aluminum, guns, etc. Not fully as shiny as a freshly polished part, but pretty good & has a good rep with shops that have used it for years.
 
I also have a powdercoated trailer that is about 7 years old, no winter towing, and sits inside. The trailer is rusting under the powder. What flakes off is paper thin.

The good powder jobs have more mils and that is what lasts. I have a 4' by 4' by 7' tall powder oven that I built for powder coating the exhaust systems for the cars I build. Other than that it gets used as a preheater for welding cast iron. For me the powder just doesn't give me the flexibility of SPI epoxy and topcoats. MIght not be quite as durable but SPI holds up well to road use.

Not to mention pitted parts aren't much fun with powder. The stuff sands out of the pits harder.

They do have primer powders out now for a prime coat that are supposed to be corrosion resistant. I haven't tried any of them.
 
Brad J.;n78896 said:
I also have a powdercoated trailer that is about 7 years old, no winter towing, and sits inside. The trailer is rusting under the powder. What flakes off is paper thin.

The good powder jobs have more mils and that is what lasts. I have a 4' by 4' by 7' tall powder oven that I built for powder coating the exhaust systems for the cars I build. Other than that it gets used as a preheater for welding cast iron. For me the powder just doesn't give me the flexibility of SPI epoxy and topcoats. MIght not be quite as durable but SPI holds up well to road use.

Not to mention pitted parts aren't much fun with powder. The stuff sands out of the pits harder.

They do have primer powders out now for a prime coat that are supposed to be corrosion resistant. I haven't tried any of them.
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primers are really nice, use them for military jobs under spray CARC and a two step powder job. saves alot of time. You just need to gel the primer at low temp if you are topcoating with powder so they will bind together, otherwise, overcuring the primer will make the topcoat chip off.
 
I worked with powder for many years. I've designed automated systems for manufacturers, I've installed and operated these systems as a supervisor, I'm neck deep in chemistry selection, application processes, pre treatment processes.... Been there, done it all, walked away from it all to build hot rods and restos full time from my home shop.

Here's what I think about powder coating.

It belongs on brand new, high volume manufactured parts. That's what it works best for. Manufacturers can design their parts for paintability (to a certain extent), they can select the proper pretreatment for them, they can design the racking and masking for high volume painting, they can select the right powder chemistry for the exposures and uses their parts will see in the real world. They can run temp data recorders with the parts through the cure ovens to be sure they are hitting cure targets.

​They can do all those things and pull off a confident and consistent coating for a low cost, safe, enviro friendly, efficient, decent quality.

That's what powder coating is for.

I've got no room for powder on my builds unless it's on some new control arms or something like that. But I'm not bringing a car frame or anything else original to the car to get powder coated, no damn way.

I've done powder long enough to know better.

There is NOTHING magical about "powder".

It's an efficient process that works well for manufacturers, but you can match and exceed the performance of "powder" with the right liquid coating efforts.
 
El Toro;n78770 said:
I feel the same as you jlcustomz.............my two car trailers 4 years old the are a rusted mess both were power coated. My brothers trailer was a factory painted trailer 6 years old looks great. Also some of the other projects just don't seam to hold up and when chiped go right to rust and then creeps under the coating. Reminds me of por-15. Looks very nice when new. Hell I painted a rusty metal metal brace for oudoor use with SPI epoxy and acrylic enamel a few years ago and still looks great even when I bent a section.
Just my opinion
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Just like with liquid coatings, prep is everything.

Manufacturers have the advantage of being able to specify substrate and or treat the substrate prior to the coating efforts. Sadly it doesn't occur to many of them that they have this type of control. In most cases where you see failures like the trailers you mentioned it is simply lack of knowledge on the manufacturing side.

There are certain metals that lend themselves more friendly to cleaning and conversion coating processes. CRS is usually very nice to work with where structural tubings with carbon scale are less awesome for a professional coater to work with, structural shapes like flat bar, angles, channels etc suck even worse.

An awesome coating on a steel framed trailer made up of structural mild steel tube and shapes (bar/angle/channel) will start with a blast spec. Shot blast is currently fairly popular because you can maintain the shot size in your reclaim cycle. A shot blast profile will typically be specified, for me as a coater what I like to see is all of the blue/black mill scale to be gone and for the blast profile to not be too damn rough.

You can also acid pickle these types of parts for removal of the scale film, acid pickles are typically submersion processes which takes a huge amount of space and forces special efforts to get the acid bath solution back out of open tubes or other pocket areas that will scoop solutions from a process tank.

The reason to remove the scale from these types of steel parts is because that layer is a weak link between your coating and the underlying substrate. A coater will likely use a spray cleaner stage to remove oils and soils from the parts, then a rinse, often times a second rinse. In the old days we would then shoot for an iron phos stage, this will most often be a heated chemical spray stage where the acidity of the stage itself leaches off a microscopic amount of iron as it in turn deposits iron phosphate molecules at the surface of the substrate. It's sort of like a plating process on a very mild scale. This will be followed by multiple rinse stages with the stages becoming increasingly cleaner until the final rinse where the TDS will hopefully be under 20 parts per million on solids.

I personally prefer the newer "nano coatings" like henkel's NT1 over old fashioned iron phos but I'm just giving a process example for the sake of showing how involved the prep can be for a truly long lasting coating.

Next is powder selection, if it's a single coat process then hopefully they are choosing something like a "supreme weathering" or "super durable" variety of a TGIC polyester. They will have film thickness standards and they will have pre tested the cure cycle with temp recorder probes attached all over a bare steel part to insure the proper temp induced cross linking of the coating.



But here's how things sometimes go rather than the above.

Bubba wipes the trailer frame down with some paint thinner until the rags aren't too black, there is no blast process. Roll it into a batch booth, blow some powder on (black powder, we really don't know anything else other than it's black) then we roll it in an oven and bake it for a while.

All the scale removal and cleaning, conversion coating and rinse processes, they remove hyper corrosives from your steel and replace them with an inert layer that promotes adhesion and prevents corrosive creeping under the paint film when chips and scratches occur. The cure is also crucial as the powder has dry blended A and B components that need to melt in order to blend and actually cross link right on the part itself as it's being cooked. The powder manufacturer will spec "time at temp". You need the powder to reach the target temp and hold for X-minutes or the cross linking will fail to occur. This is where you get a paint film that flakes off like potato chips, under cured powder. You can and will have cured and under cured powder on the same part due to heat sink areas. Thicker heavier areas will take longer to get up to temp.

It costs money to do it right. And typically you will only see it done right in big name brand manufacturers that have been in business for many years and care to continue in business for many more.



I would not be bringing a hot rod frame or other parts to a custom powder coater with the idea in my head that they are going to do do a better coating job than I can do in my liquid spray booth in my shop.

Now If I was forced to bring a hot rod frame to a powder coater because my customer was irreversibly mesmerized by the word "powder", then I would be there with the powder coater observing the cleaning and prep process as well as insisting on a dry cure test or two with heat probes attached to record substrate temp/time for the bake cycle.

I would do all that to help protect my customer from expensive paint failures, I'd also say a prayer or two and cross my fingers.

"OK smarty pants, what would you do instead of powder coating then?"

I'd prep the parts, likely with a blast profile, I would clean the parts per prep instructions that can be found here at SPI and coat them with SPI epoxy followed by a high solids single stage 2k urethane, formulated in the gloss level and color that the customer requires.



And now I offer apologies. lol

I'm too new a guy here to be posting a lengthy tech type rant.
 
No apology needed. You are the expert in this area and there is no telling how many people you just gave a very detailed education to, me being one of them. Having never done powder coating it opened up my eyes and mind to just how detailed it has to be to last. I learned something new today. Thank you.
 
Well, thanks. But I still worry about stepping on toes because I'm sure there are experienced powder coaters here that are smart enough to do a good job of it.

To be fair to those guys, I'll give a view from the coater's prospective.

I ran a powder operation for many years, we did so with great confidence every day of the week because we had redundant controls on all of these crucial variables.

I would get people bringing me all kinds of strange old junk, wanting me to make it all better with the magic powder sprinkles.

I hated that.

When somebody brings you an old part or maybe a hand fabbed new part that they are all proud of, they have the best intentions because they believe "powder" is superior to all coatings.

But as a coater, you know very little about the part, where it's been, what sort of contaminants are on it. Rust pits, grease, silicone, old paint, permanent marker, strange oils.... and it's something that was not designed to be heat cured. It's got thick intersecting weld joints that make huge heat sinks and it's also got thin metal areas that will come up to temp very fast. It's got brackets and deep channels that are nearly impossible to electrostatically coat with dry powder because of faraday effects of the deep draws and inside boxed areas.....

The powder coater is automatically at a huge disadvantage because of all these things.

The difference is some guys know of all these concerns and others do not. Usually the guys putting out work that fails on someones hot rod or custom build, they honestly think they are doing things right, they just don't know enough.

The guy that knows his stuff is going to either be super expensive because of all the hoops he has to jump through, or he's going to be losing money because of his extra efforts to do a decent job on your parts.
 
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