Date: Wed, 22 May 1996 06:34:12 -0500
From: Dave Wright
At 08:10 PM 5/20/96 -0700, you wrote:
>Another question for the group: I would like to hear your pros and
cons
>on powder coating vs. painting (and types of paint). People have told
me
>don't powder coat anything that will flex or bend as this will cause
the
>powder coating to crack. It seems to me that there aren't any parts
on
>a bike that won't experience at least some bending or stress, so this
>doesn't make sense to me.
>
>As I am going to strip my Commando to the frame I want to get it either
>painted or powder coated and don't know which costs more or which
is
>better. Ideas and comments?
Kurt, let me explain a little bit about the coating processes, as finishing is my business.
First whether you are spray painting or powder coating, you are simply looking at different *methods* of applying an organic film. Each has some inherent advantages, but for our purpose powders main advantage is the ability to lay down a thicker coating of the finish. Typical spray paint films run .7-1.2 mils (thousandths in painters terms) and powder films run 1.0-2.5 mils. Powder is or can be just as flexible as wet paint. I can show you panels that have been powder coated or wet painted that can be bent back and forth until the metal fatigues and breaks, yet the coating will not flake away. This is a property in the coating by the manufacturer.
To throw another option (read = opportunity for flames!) in I would look for someone in the area that can acrylic (< important, not epoxy) electrocoat (aka E-Coat, Electrodeposition) your frame. E-Coat is a method of dip painting in paint that is actually plated on with current, like chrome plating. E-coat has the ability to penetrate all areas and leave a coating. BMW has gone to electrocoat for their frames.
The most important thing you do is surface preparation. That metal need to be squeaky clean if you want any of those coatings to stick. Any quality shop that does the process will do it for you (let them!) and usually apply an iron or zinc phosphate.
Let me know where you are and I might be able to provide some sources.
__________________________________________________________________________
Dave Wright
Mequon, WI
'73 Norton 750 Commando
'79 BMW R100
Date: Wed, 16 Oct 1996 16:06:08 EDT
From: Derek Matheson
Tea-time begins . . .
There are two basic type of powders used in powder coating, both electrostatically
"floated" onto the part surface as described. First and most common type
is powdered thermoplastics (nylon, Teflon, polyester, polyethylene, PVC,
polypropylene). Others are thermosetting plastics and epoxies, the "drying"
happens when the chemicals in the compound reacts. With the thermoplastics
(read nylon), you're enclosing the part in an essentially waterproof coating.
Problem is when the surface is cut, this creates a very small anodic point
for corrosive action. That's why the garden furniture rusts so well - the
stuff cracks at the joints and water gets in.
With thermosetting powders (the stuff that they use to continuously coat coils of metal used for washing machines, fridge's, etc, this is somewhat permeable, and the water can evaporate off. Is a rust inhibiting basecoat is still required? Then if the stuff does get chipped off, there's some residual protection. All the bolt on parts for my Bonneville were cadmium plated, etched, primed and epoxy painted. At the time, I could have had them epoxy powder coated, but didn't, because I knew that I would repaint later on and would then use the epoxy as a base coat.
The powder chappie told me that paint would not stick to the powder
very well because of the plasticizers in it, which would migrate to the
surface over time.
OK, tea-times over.
Derek
Following has reference:
>[and then Falco again:]
>We exchanged messages off-line yesterday on this, but for the benefit
(or
>detriment) of Brit-Iron, a short summary of my response is: "I'm sticking
with
>my opinion." In brief, powder paint is made up of, yes, powder, that
is
>electrostatically applied to the piece to be coated, which is then
heated to
>melt the little plastic pellets. This results in a coating that is
relatively
>thick. To date, no powder paint has been developed that, to my eye,
does a
>reasonable job mimicking "real" paint.
>[snip]
>
>The powder coating done by Essex Motorsports on my swing arm and triple
clamps
>looks fabulous. The many lumps and flaws in the triple clamps show
up perfectly
>through it! Pretty and shiny as any "real" paint job I've ever seen,
and
>immeasurably more durable.
>
>According to the reading I have done, the powder is composed of the
same
>pigments used in wet paint; the difference is only that they are not
diluted
>with solvents that must evaporate after application. An electrostatic
charge
>is used to attract and bond the powdered pigment rather than spraying
the
>pigment in solution.
Date: Wed, 16 Oct 1996 19:05:06 -0700 (PDT)
From: Eric William Lamberts
On Wed, 16 Oct 1996, Refrigerator Johnny wrote:
> hello all!
> I've been restoring/customising a '78 Bonneville on and off now for
two
> years. It's been slow. I've got the bike stripped down, and am ready
to
> paint the frame. All though I have an air compressor, I have decided
to use
> spray cans for ease. This is my plan:
> sand blast down to bare metal.
> apply two coats of primer (wet sand after each application.
> apply X coats of high gloss black.
> apply Y coats of clear high gloss.
>
> I am planning on using Rustoleum products (I've seen Krylon also).
> Is my plan majorly flawed? Can I expect great/good/crap results using
spray
> cans?
> Forgive me if this subject has been covered - it's hard to keep the
> brit-iron inbox clear!
> -johnny
I've painted a few tanks with spray cans. They look great, but the durability is poor. In spite of careful prep, they have a tendency to flake with minimal trauma, and don't seem to have much gasoline resistance, neither to Oxy fuels, or the summer non Oxy. They end up not looking so good within a few weeks of use.
A better plan would be to go to your local auto paint dealer and buy
some catalysed enamel. This has to be mixed with a catalyst, but dries
durable and fuel resistant. Imron is very good, but quite dangerous to
use--I would not use it unless you are very familiar with it's hazards
and have full protective gear. At least in this state, Nevada, I don't
think you can even buy it
]without special certification. The down side to catalysed enamel is
that you have to buy stuff--spray gun, water trap, pressure regulator,
masks, etc
Eric Lamberts
'72 Commando
'75 RE5
'78 UJM GS750
'71 X6-another UJM
Lotsa other stuff