DIYbanter - View Single Post

In article ,
says...
On Thu, 12 May 2005 07:16:48 +0100, Paul Mc Cann
wrote:

Powder doesn't really differ from ordinary paint with the exception of
the use of an electrostatic charge to assist the particles adhere to the
surface prior to stove enamelling.

That's electrostatic spraying.

Precisely

You're applying what's basically standard
paint, but the static charge improves coverage especially round the
back, on corners and in shadowed areas. For flat sheet it's no better
than a simple spraygun, but it's a good improvement for complex shapes
(such as gates).

I'm afraid you are only confusing yourself again. Powder coating is
applied electrostatically exactly as I said

Powder coating is "coating with a powder", pretty much by definition.

The powder is only a type of paint in a powder form. Its a mixture of
resins and colouring compounds. (i.e.) Paint. It flows out when heated.

slightly sticky _powder_ is sprayed with an electrostatic gun,

as I said originally

then it's
heated in a stove enamelling oven and only then does the powder fuse. If
you limit this fusion time, there's enough fusion to make it stick, but
not enough to make the surface glossy. You're thus a bit at risk of
operator skill here - too little fusion gives a guaranteed matt without
shiny patches, but it can also be porous (usually on the bottom edges of
rails)

Its not rocket science any half trained operator can control the
application. If your local shop can't do it then find one that can.
Personally we use several different commercial sprayers to spray and
stove enamel steel frames, and have used many different shops over the
years. None had any problems in this area.

Dipping is similar to powder coating, but it's done by dipping in a
fluidised bed of powder (a bucket, with air blown through the bottom).
It's reasonable to describe either as "powder coating", unless specified
in more detail.

No. Your confused again. Dipping is mereley dunking in paint. Specially
formatted paint/lacquer given, but essentially just liquid paint. It can
give a very heavy coat, hence its popularity, but improper substrate
preparation can lead to quick deterioration and delamination. Most paint
brush handles are dipped.

The problem with powder coating is similar to that of Hammerite - the
coating itself is far stronger than the adhesion to the substrate.
If you annoy it, it loses the bond and you get the coating peeling off
wholesale. Dipping gives a thicker coat, so it's more prone to this.
However sprayed powder coatings can be thin on edges, so they may be
more susceptible to wear and the first delamination starting.

I really don't know where you are going with this. There is very little
valid comparison to be made between a powder coated stove enamelled
finish and air dryed Hammerite. The adhesive properties of any paint are
primarily down to the proper preparation and etch priming, if necessary,
of the sub strate. The thickness of the coat has little relevance to the
bond strength. Electrostatically applied coatings excel on edges due to
the nature of the application

Personally I'd much rather hot-dip galvanise a gate, then let it weather
on its own.

Its apples and pears. While I would agree that galvanising is a much
better protector of steel than paint its unreal to talk about
galvanising and any of the readily available paint processes in the same
breath.

Back to the o.p. Personally I think a powder coated stove enamelled
finish was the next best thing to galvanising. The dulling/greying of
the paint may be down to the quality of paint used and the actual
colour. Darker colours and reds will show these tendencies quicker than
most.

--
Paul Mc Cann