1970 Plymouth Rebuild: Powder Play

A botched wheel order forces us to take matters into our own hands with powder coating to make it right

*Part 8 of our series on rebuilding a 1970 Plymouth. Read Part 1 here.

 

I can see that he’s telling me all about powder coating, since his lips are moving, but no words are coming out of his mouth.

They’ve been replaced by the ringing in my ears.

It’s not the first time Marcel Allain has slammed together two hollow aluminum cylinders — the kind used to carry oxygen — to show just how tough the powder-coated finish is. It’s his standard demo. Here he goes again… uh oh.

“CLANNNNNG!”

“See? It didn’t even leave a mark.”

Allain, also a body and paint professional, speaks with supreme confidence — even if I can’t hear a word of it — and rightly so, given his lengthy experience coating everything from office-building hand railings and motorcycle frames to the centres of the three-piece Project Plymouth wheels.

As you might recall from the last instalment, our first wheel order (yes, there is a second wheel order coming down the road) had been seriously botched, arriving with a skinny rear lip and bling-bling chrome instead of grey.

Inexcusably, and inexplicably, the wheel company would not own up to the colour mistake, but it did exchange the rear inner and outer hoops, which — against their strict in-house quality-control policy — they allowed me to swap.

So, apart the wheels came; the chrome centres were sent to Allain while the new inner and outer rear-wheel halves from the supplier sat on the bench at the East Coast Garage.

 

Powder coating a common practice in the auto industry

Powder coating is a painting process, according to Allain, that’s used in the auto biz by everyone from original-equipment manufacturers to the makers of aftermarket hardware, from roof racks to wheels and suspension parts.

 

 

Simply put — really simply put — the process involves lightly blowing a plastic powder onto a metal part and curing it in an oven. It goes a little something like this:

1) Prepare the part (usually by glass-beading, which means pummelling the part with gritty stuff propelled by compressed air) and then give it a thorough wash with solvent. As with liquid painting, this process is crucial to a quality finish.

2) The part is hung from a metal rack that’s hooked to a ground wire.

3) A special sprayer gives the plastic powder a positive charge. It’s lightly blown over the parts and sticks, much like dust to the static of TV screen. Unlike liquid painting, if you’re not happy with what the part looks like at this point, dust it off and start over.

4) Moving the parts around won’t dislodge the powder, but physical contact will. Don’t touch. The rack holding the part is carefully wheeled into a propane-fired oven of the appropriate size, even big enough for the frame of a car.

5) Often incorrectly referred to as ‘baking’, the powder is actually ‘cured’ with heat, which is where it gets its gloss (if that’s the type of finish you’ve specified). Depending on the thickness and size of the part and what it’s made of (steel vs. aluminum, for example), the cure time varies, but generally takes no more than 30 minutes. The clock begins running when the part — not the air in the oven — hits 400 F (204 C).

5a) Parts that can’t stand the heat cannot be put in the oven — including plastics and rubber pieces attached to metal parts — and even some softer metal parts.

6) Air cool and enjoy.

 

Properly done, the benefits of powder coating are numerous.

“It’s used on snowplow blades with minimal wear, so it must be good for a set of wheels.”

Surfaces that shouldn’t be coated — areas that need to stay bare — need to be masked off using special high-temperature tape. Likewise, bolts or high-temperature plugs are an absolute must to prevent coating the threads.

And like many things, you get what you pay for.

The Plymouth’s wheel centres were labour-intensive to prepare since the chrome needed to be hand-sanded after bead blasting. Allain’s price was $150 each plus $100 for the powder, which was a special order since colours can’t be made or mixed onsite. Still you can get just about any colour/finish you want (even metallics), even if it means providing a sample to match.

 

At the right is what I got even though it’s not what I ordered. At the left, after remaking the wheels for the right size lip, powder coating the centres and modifying the caps to fit flush.

 

Reassembly of the wheels involves sealing the inner and outer halves with silicone caulking and carefully threading the three dozen bolts back into place and gradually torquing them in sequence.

Each wheel took one evening in front of the TV to reassemble. Remember, all this work, time and cost were due to a simple and preventable error by the wheel company, which it would not make right.

Ultimately, the effort was for nothing. I just couldn’t warm up to the wheels. In a future instalment, you’ll find out what I did choose and why, and also what real customer service looks like.

So, with that out of the way for now, it will soon be time to change gears and bring you up to speed on the Project Plymouth’s 1,000-plus-horsepower engine.

 

 

The complete series on the 1970 Plymouth Rebuild:

Read Part 1 of the 1970 Plymouth series here.

Read Part 2 of the 1970 Plymouth series here

Read Part 3 of the 1970 Plymouth series here.

Read Part 4 of the 1970 Plymouth series here

Read Part 5 of the 1970 Plymouth series here.

Read Part 6 of the 1970 Plymouth series here

Read Part 7 of the 1970 Plymouth series here.

Read Part 8 of the 1970 Plymouth series here. (You are here)

Read Part 9 of the 1970 Plymouth series here.

Read Part 10 of the 1970 Plymouth series here.

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