Author Topic: Frame finish: Lacquer vs Powder-coat  (Read 10510 times)

0 Members and 1 Guest are viewing this topic.

Offline MrWright

  • Full Member
  • **
  • Join Date: Nov 2005
  • Posts: 56
Frame finish: Lacquer vs Powder-coat
« on: 21 Mar 2006 at 02:48 »
Should I finish the frame (1947 T35) with lacquer or powder-coat?  I know it sounds trivial, but I am torn.  Powder-coat has its advantage, but touch-up is not one of them.  When it gets chipped, it requires strip and re-finishing.  It is, however, durable.  Lacquer, one the other hand, is easy to finish, and refinish.  And, it yields an authentic look.  I appreciate any advice from follow Douglas members.  Added note: I will spray the lacquer myself, having done so many times.  I guess I’m just getting caught-up in a quandary between what I have done, and what is current practice.  Side note: the tank, fenders, headlight and details will be black lacquer.

Dave

Offline trevorp

  • Master Member
  • ****
  • Join Date: May 2005
  • Posts: 502
  • Location: Australia
Re: Frame finish: Lacquer vs Powder-coat
« Reply #1 on: 21 Mar 2006 at 02:52 »
Im at this stage with my mk1 aswell and im thinking of painting in acylic  myself although im tempted to powder coat
so ill be needing the same advice

Offline MrWright

  • Full Member
  • **
  • Join Date: Nov 2005
  • Posts: 56
Re: Frame finish: Lacquer vs Powder-coat
« Reply #2 on: 21 Mar 2006 at 03:08 »
Trevrop,

One of the biggest obstacles I have run into involves the forks.  The seals at the suspension arms would not come off without damaging the rubber portion.  This means that the forks could not be powder-coated without damaging the seal (the heat is to great).  This isn’t all bad, because even tough the finish of powder-coat has improved, it is not to be confused with a lacquer finish.  Second, the heat from the powder-coating process may have some stress-relieving effect on the frame.  I know that years of vibration have probably reduced much of the internal stresses, however, heat even at the low levels of 325-375°F, however, it is never “all gone” without heat (re-arranging the molecules).  I talked with my local media-blast shop and they are going to use a plastic media for my forks, assuring me that any media which may intrude into the bearing areas will breakdown in the presence of grease and oil.

Offline MrWright

  • Full Member
  • **
  • Join Date: Nov 2005
  • Posts: 56
Re: Frame finish: Lacquer vs Powder-coat
« Reply #3 on: 21 Mar 2006 at 03:11 »
PS:

Nice reference attached (no relation to me)

Dave

www.my.execpc.com/~davewrit/Powder.html






Offline Doug

  • Administrator
  • ****
  • Join Date: Mar 2004
  • Posts: 3963
  • Location: Glen Mills, PA, USA
Re: Frame finish: Lacquer vs Powder-coat
« Reply #4 on: 22 Mar 2006 at 04:34 »
I have been using acrylic urethane 'enamel' (such as DuPont Centari.) It handles much like lacquer in the preparation, application, and clean-up. You do lay it on a little thicker so that it flows out, rather than the multiple build-up of feather thin lacquer coats. So runs can be a problem, as well as overspray, as you can not sand/buff them out. You do have to modify your spraying technique accordingly. Some enamels have a gloss activator, that accelerates the cure and allows some buffing/compounding, but not quite like what you are use to with lacquer. Most of the additives or two-part paints are carcinogenic. The one gripe I have about the regular line of acrylic enamels is they seem to be formulated to induce some orange peel, I think to match the factory finish on cars, in the repair business. I have not tried the high end enamels that likely do not have this characteristic. I have heard of folks paying $800US for a gallon of a particular shade of orange for their custom car. DuPonts high end paints, like the ChromaSystem (another acrylic urethane), are touted as being suitable for spot repairs. Of course, they say all their acrilic ureathane paints flow out smooth and perfect! 

I have rather come to dislike lacquer primers, especially for frames, as it chip too easily, taking off the top coat with it. I find DuPont "Corlar" epoxy polymide primer quite good for painting frames.  No matter how thick you apply it, it will cure! Good for filling pits from rust and sanding back, but it is tough to sand. Best done wet/dry silicon carbide paper, flushed with water. It is quite tenacious, and impervious to water or air once cured, so if you do have any residual rust it does not spread. I have painted it on rusty metal that has been left exposed (my old truck), and about all it does is fade a bit with time. The pigments settle out in the can rapidly and solidly, and it is a bear to mix. But it will after half an hour with a paddle and an electric drill.  Oh, and it is really carcinogenic.

Also seen some experimentation with "Por15", a conversion moisture cure primer. It too is good at encapsulating rust and strangling it from further oxidation. Only seen it used it on sandblasted parts, mostly, and it can be a bit slow to cure on dry days. Moisture in the can can cause it to 'kick-off' and gel. Though available in black, it needs to be top coated as UV light seems to degrade it, and it weathers heavily if left exposed. But again, I have not seen rust bloom through it on my old truck. My old truck is the recipient of any left over dregs of paint in the bottom of the can! UV is about the only thing that seems to affect it. It makes a very hard, durable surface. In fact, I am not sure you would want to use it on a rough surface as sanding it just wears out the sandpaper! It does not seem to be any more toxic than old fashion lacquer.

If using Por15, and you need a filler primer, the new polyester primers seem quite good. They build quickly, dry fast, and sand easily, yet seem durable rather than brittle like the old lacquers. They are softer, so not so good under areas than things clamp to with a lot of pressure, especially if you have a lot of build (applied thick.) Which is why I prefer Corlar despite it being more difficult and expensive.

I would steer clear of DuPont Imron, a polyurethane. My father tried it on a motorcycle frame as it was promoted to be tough and chip resistant. It chipped just like anything else. A friend had his small airplane painted in Imron, and it chalked-out quite badly sitting in the sun. But it would buff right back to a brilliant luster very quickly, much quicker than enamel would have. Not very relevant to a motorcycle frame. The polyurethanes are also a two-part paint, and are highly carcinogenic.

Also seen some motorcycles parts powder coated, but they tended to look 'plastic encapsulated' Mainly small bits like hubs and rear stands where the chip resistances was figured to be a plus. One downside is there is not much you can do in the way of fixing surface defects and pitting. Any filler has to be able to take the heat to cure the powder coat. I have heard tell of folks that powder coated a frame, and had problems were clamping pressures were applied. The powder coat flowed and extruded out from under washers, fasteners, and clamps, forming and unsightly 'pressure ridge'. So places where the engine mounts should have the powder coat sanded off.

I am not actually a big fan of DuPont paints, and I think they charge way too much, but it is readily availble at the local automotive refinisher supply.

-Doug

Offline MrWright

  • Full Member
  • **
  • Join Date: Nov 2005
  • Posts: 56
Re: Frame finish: Lacquer vs Powder-coat
« Reply #5 on: 22 Mar 2006 at 05:22 »
Great info Doug.  I have read confirming info on much of what you wrote.  I had the chance to “play” with powder coats as an automation engineer back in Detroit (go Red Wings) and the down-sides were plenty.  Basically, powder-coating is a reflow-thermal-set plastic, which binds mechanically to the surface.  I have seen first hand, in life cycle testing, where moisture “gets under” the coating and produces problems.  This is why the surface MUST be media blasted to produce the correct surface finish for binding.  I am not anti-powder-coating; however, there is a place and time for everything.  I just don’t want a “plastic-dipped” finish on an old English bike.  Over-restoration is way-too common.