This thread has come up again only a few weeks since we last addressed
it,
and since there are apparently a number of new people that did not get
this
information the first time, I apologize for reposting it to the whole
list.
However, it seems that there are some out there that will benefit. I
also
have since had some powdercoating done on some pieces and have the
following additional comments:
Make sure all surfaces that could be damaged by sandblasting or should
not
be powdercoated are very clearly marked ON THE PIECE. Verbally telling
the
shop manager what should and should not be coated did not work.
Unfortunately, some bearing surfaces were damaged by sandblasting and
some other areas had coating that had to be removed. Disassemble
EVERYTHING down to the last nut and bolt. It will be difficult and
destructive to get it apart later if you need to. Try to clean up every
possible bit of oil and old grease from INSIDE the part. The heat tends
to liquify grease and it will ruin the coating where it leaches out.
Sandblasting and OUTSIDE cleaning will be done by the shop.
I was pretty pleased with the final result. It looks good and should be
very durable. The cost was more than I expected, however, since the
price goes up based upon the amount of handling required for masking,
etc. The chassis itself cost $175, while a bunch of smaller parts for
the suspension ended up costing $125 (about sixteen pieces, including the
axle u-bolts, one side of the front suspension, the front springs, etc.).
If anyone out there thinks these prices are a rip-off, please let me
know, because I intend to get some more work done at this place.
It does go on very thick compared to paint. This is good if you have
some surface imperfections, such as acne from rust or scratches,because
it will become smoother (not perfectly smooth in all cases, however), but
it is bad for fine detail, such as chassis number stampings, that can
become partially obscured. You will likely need to do some chasing of
threads and certainly trimming of the material around threaded holes,
since the material tends to "climb" the plugs and create some "flashing"
around the holer. The material is not as consistently applied as I
thought it would be, it tends to cling on edges (due to surface
tension?), so it can be thicker in some places than others.
NOTE: THE FOLLOWING WAS PREVIOUSLY POSTED ON 1/2/97:
The following is a definition I picked off a website somewhere, sorry to
post something this long to the whole list, but perhaps it will help
others. I was researching the issue myself because I intend to have my
TD chassis powder coated. As a matter of fact, I spent New Year's day
stripping off the chassis. I will let the list know about the results.
I haven't done any myself yet, but this is what others have said: Pros--
a hard, smooth surface almost impossible to chip, no drips, no runs, no
errors, extremely consistent application (no thin or missed spots due to
electrostatic application), environmentally friendly because no solvents
are used. Cons-- If you get it where you don't want it, like in a
threaded hole (they mask these beforehand, but they might miss one) it is
very difficult to remove. It has the same hardness as paint and so it
will scratch about as easily. It goes on thicker than paint so be
careful what you get coated-- it might cause problems for things that
require a close tolerance.
Cost? I was quoted between $150 and $175 to do the chassis, including
sandblasting. The price list I got said about $40 for a wheel and
between
$5 and $20 for smaller parts. When you consider paying for sandblasting,
epoxy primer, and paint separately (plus someone else's labor), it seems
very competitive.
Hope this helps. Here comes the definition:
What is Powder Coating?
Powder coating is an environmentally friendly alternative to solvent
based
paints (and in some cases plating). The powder is made of dry, finely
ground organic resins and pigments. The powder is most commonly applied
by spraying with a gun that electrostatically charges the powder as it
exits the tip. In most cases, the powder is applied directly to a clean,
bare metal surface, with no primer or base coat (powder coating can also
be applied to glass, ceramics, temperature resistant plastics and even
wood). The part that is being coated is electrically grounded, causing
the charged powder to cling to it. After coating, the part with the loose
powder clinging to it is placed in an oven to cure. In the curing
process, the powder melts and flows over the surface of the object
without drips, runs or sags. The result is a highly durable and
attractive finish in a wide variety of colors, glosses and textures.
------------------------------------------------------------------------
Why Powder Coating?
Because of the need to reduce the introduction of air pollutants and
hazardous waste into the environment, a variety of alternative methods
for
applying finishes to products are being developed. Chief among these new
methods is powder coating. Powder coating needs no VOC's (volatile
organic compounds) in any part of the process. This eliminates one of the
major
causes of air pollution today. The most common coatings are made from
polyesters, urethanes or epoxies as a base. These are stable materials
that have extremely low or no volatile organic compounds. Powder coating
is also an economically attractive process. Because there are no
volatiles, the air in the work area does not have to be vented outside.
This can offer significant savings in heating and cooling costs. Also,
with conventional solvent based coating methods, overspray is wasted
material. Powder overspray on the other hand can be collected and reused,
thereby achieving
95 percent and greater usage of materials.
------------------------------------------------------------------------
Where is Powder Coating being used?
Chances are you have quite a few things at home that have a powder coat
finish. It is used extensively on many consumer products such as
appliances, furniture, fixtures, automotive parts, sporting goods, etc.
Commercial applications include store fixtures and office furniture. It
is
used on farm implements and in many industrial applications where
durability and high resistance to chemical and environmental stresses are
needed. Powder coating can also be an excellent choice for refinishing
projects such as bicycles, motorcycles, automotive parts, indoor and
outdoor metal furniture, etc.
------------------------------------------------------------------------
Preparing Your Project For Powder Coating
The coated parts are cured in an oven at up to 450 degrees F, for up to
30
minutes or more. Any part of your project that cannot withstand this time
and temperature exposure must be removed before coating. This would
include
foam insulation, rubber pads or gaskets and plastic pads or attachments.
Because powder adheres electrostatically, it must be applied to a very
clean surface. It will not cling well to old paint, primer, most metal
fillers or rust. Chemical stripping and/or bead blasting of the surface
is recommended. Sand blasting with coarse media can leave a rough
textured surface that can show through the finish and in some cases cause
gassing that leaves pin holes. [Note: My supplier PREHEATS the material
to be coated, he says this reduces pinholes] Any welds, ripples, dents
or pits on the metal surface can show through the coating after the
powder is cured. If you want
the finished surface to be free of these types of imperfections, they
must be smoothed or removed before the powder is applied.
David Littlefield
Houston, TX
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