Sorry, I forget to say that the plating is for a 40' steel sailboat
Regards,
Jesús

After some inquiries, I've found that the ceramic component in the
primer is intended to facilitate the welding. But I still don't know
which is the optimal thickness; my fear is that should the plate be
primed with too thick a coat, the pattern left in the plates after
the steels's sandblasting may not be sufficient for the following
epoxy coats to "grip" on the steel.
Regards,
Jesús

On 2 Jul 2003 12:07:02 -0700, (jalborey) wrote:

After some inquiries, I've found that the ceramic component in the
primer is intended to facilitate the welding. But I still don't know
which is the optimal thickness; my fear is that should the plate be
primed with too thick a coat, the pattern left in the plates after
the steels's sandblasting may not be sufficient for the following
epoxy coats to "grip" on the steel.
Regards,
Jesús


I am not quite sure of what your up to here.

Primer is Primer - as in its there to save you doing it.
But I don't know the steps they followed - did they degrease, then do
an acid etch - prime and bake in on - Maybe the stuff is quite hot
shot especially as its zinc loaded.

You can buy steel with various pre coated surfaces depending on your
situation - Are you building this thing outdoors, is rust a problem?

But you have an alternative Paint system worked out, and your going
to sand blast it anyway ?

As for paint thickness, if its a hard paint - less is best unless its
a self cleaning paint, (sheds its outer surface), soft paints are
better a little thicker - they squash up more on impact -
The hard paints chip, especially on edges - and if has a hard surface
underneath - also it cracks as stars
It depends on the resins and the fillers, type amounts etc.
But it depends on the type of paint some more flexible than others.
Which depends on its working environment - its always a trade off -$$$
come into it too.

But it seems your only going to sandblast it off anyway.
While it may be easier to sandblast of the rust - if its only slight,
this gives it a key at the same time - But it seems you need to do
more home work on this.- They should have more specs on this as to
what they have done and the coatings you can go over it with.
You need to talk with the technical folk, not the sales staff - but
they should have hand outs.

Some steel comes coated with a sacrificial coating - but this one
seems to be a bit more elaborate.
You still left out to many points - you have to do more homework.

I seem to remember the "yard birds" using I think it was Zink Chromate as
the bare metal primer on the hull and any steel hull components. Must have
done some kind of metal etching as they were dressed in full Hazmat gear.
I know it was a dirty yellow. (Er, that was a nuke sub, BTW.)

"jalborey" wrote in message
om...
Rational(?),
thanks for your answer. I regret to say that I haven't explained
myself very well. I don't intend to sandblast again the hull after
completion (only grinding and touching up the cuting and welding areas
as required); the steel comes sandblasted and preprimed from the mill.
That's why I'm trying to ascertain the optimal thickness of a primer
coat which I intend to use as the first layer of the paint scheme, as
well as for protection during the building process (I'm going to build
outdoors, but in a dry climate). As the main protective coat I will
use epoxy tar. As the top, cosmetic coat, I intend to follow the
advise of the epoxy tar provider.
The steel provider -which is a mill working for the naval industry,
and not used to the somewhat different requirements of small craft--
serves the plate preprimed with a wide range of thicknesses for the
primer coat, and that's where my doubts arise from. May too thick a
primer coat prevent a correct mechanical grip between the preprimed
steel and the following coat?
I've contacted a couple of coating industries in my area, but they
haven't give me a totally satisfactory answer. I've send my question
via email to other paint providers, but still to no avail.
Thanks again,
Jesús



I am not quite sure of what your up to here.

Primer is Primer - as in its there to save you doing it.
But I don't know the steps they followed - did they degrease, then do
an acid etch - prime and bake in on - Maybe the stuff is quite hot
shot especially as its zinc loaded.

You can buy steel with various pre coated surfaces depending on your
situation - Are you building this thing outdoors, is rust a problem?

But you have an alternative Paint system worked out, and your going
to sand blast it anyway ?

As for paint thickness, if its a hard paint - less is best unless its
a self cleaning paint, (sheds its outer surface), soft paints are
better a little thicker - they squash up more on impact -
The hard paints chip, especially on edges - and if has a hard surface
underneath - also it cracks as stars
It depends on the resins and the fillers, type amounts etc.
But it depends on the type of paint some more flexible than others.
Which depends on its working environment - its always a trade off -$$$
come into it too.

But it seems your only going to sandblast it off anyway.
While it may be easier to sandblast of the rust - if its only slight,
this gives it a key at the same time - But it seems you need to do
more home work on this.- They should have more specs on this as to
what they have done and the coatings you can go over it with.
You need to talk with the technical folk, not the sales staff - but
they should have hand outs.

Some steel comes coated with a sacrificial coating - but this one
seems to be a bit more elaborate.
You still left out to many points - you have to do more homework.

On 4 Jul 2003 08:26:23 -0700, (jalborey) wrote:





In your case go the thicker coat - it gives you more meat to sand off
and degrease when you are ready for it-

It will oxidise, so you want to sand off this layer, which will then
take it down quite a bit . The longer its outdoors, the more oxide.

You need to think more in mechanical performance than just plain
adhesion - some paints systems are centered around abrasion resistance
- Such as cars which get polished a lot - so they go for a hard
surface - But for impact you want a soft "rubber"surfact - self
healing - and for some others a sheading or self cleaning - system -
But for a primer - its as much about the acid etch - as this really
bites into the metal, better than just a surface scratching.


A simple test for your primer - just give it a tap with a ball
hammer, observe how it flattens and dents, and how much it can take -
- and or it breaks away from the surface - if the "decreasing" has
been done well - it should just squash up and give an impression - but
if it breaks away, its a warning something isn't right. you can also
score a piece, with a knife, to see if you have a nice V shape -or
again it lifts and crumbles on the edges - this can indicate too much.
filler in the paint, not applied properly, or not cleaned, prepared
properly. - or too much paint on.

Also the ceramic in the paint only goes a small way to solving the
welding problem - What happens is the hot metal fries the paint so you
have this zone near the weld- if you cannot hold your hand on it -
then the paint in that area is stuffed - so it pays to check how far
back you sand- before the paint lifts on you - ceramic in the paint
only gives you a little extra - You can use modeling clay -
put some in a bucket, for when you ready to weld slap a roll of this
on your paint - to suck up the heat - it will wash off and you can
reuse it- easier to use than chill bars - But check the edge of the
paint for scorch marks and crumbling - until you get back to the good
stuff. The wet clay can slow the paint burn down.

Hello:

Industrial contractors typically have to meet a three coat spec - a zinc rich
primer, an epoxy intermediate coat and a 2 part linear poly topcoat. -
Assuming one coat of each, (topcoat probably needs two coats) I costed out the
system at under $1 per square foot....

Note that the epoxy and the zinc primer (there are several different zinc
primers) both work to prevent corrosion (rusting) each in its own different
way. I think many boat owners skip the zinc primer and just coat on the epoxy -
which is probably OK to, but requires a much better grade of epoxy than the
$0.80-$1 system quoted above.



paul oman
www.epoxyproducts.com/marine.html



Fred Williams wrote:

I seem to remember the "yard birds" using I think it was Zink Chromate as
the bare metal primer on the hull and any steel hull components. Must have
done some kind of metal etching as they were dressed in full Hazmat gear.
I know it was a dirty yellow. (Er, that was a nuke sub, BTW.)

"jalborey" wrote in message
om...
Rational(?),
thanks for your answer. I regret to say that I haven't explained
myself very well. I don't intend to sandblast again the hull after
completion (only grinding and touching up the cuting and welding areas
as required); the steel comes sandblasted and preprimed from the mill.
That's why I'm trying to ascertain the optimal thickness of a primer
coat which I intend to use as the first layer of the paint scheme, as
well as for protection during the building process (I'm going to build
outdoors, but in a dry climate). As the main protective coat I will
use epoxy tar. As the top, cosmetic coat, I intend to follow the
advise of the epoxy tar provider.
The steel provider -which is a mill working for the naval industry,
and not used to the somewhat different requirements of small craft--
serves the plate preprimed with a wide range of thicknesses for the
primer coat, and that's where my doubts arise from. May too thick a
primer coat prevent a correct mechanical grip between the preprimed
steel and the following coat?
I've contacted a couple of coating industries in my area, but they
haven't give me a totally satisfactory answer. I've send my question
via email to other paint providers, but still to no avail.
Thanks again,
Jesús



I am not quite sure of what your up to here.

Primer is Primer - as in its there to save you doing it.
But I don't know the steps they followed - did they degrease, then do
an acid etch - prime and bake in on - Maybe the stuff is quite hot
shot especially as its zinc loaded.

You can buy steel with various pre coated surfaces depending on your
situation - Are you building this thing outdoors, is rust a problem?

But you have an alternative Paint system worked out, and your going
to sand blast it anyway ?

As for paint thickness, if its a hard paint - less is best unless its
a self cleaning paint, (sheds its outer surface), soft paints are
better a little thicker - they squash up more on impact -
The hard paints chip, especially on edges - and if has a hard surface
underneath - also it cracks as stars
It depends on the resins and the fillers, type amounts etc.
But it depends on the type of paint some more flexible than others.
Which depends on its working environment - its always a trade off -$$$
come into it too.

But it seems your only going to sandblast it off anyway.
While it may be easier to sandblast of the rust - if its only slight,
this gives it a key at the same time - But it seems you need to do
more home work on this.- They should have more specs on this as to
what they have done and the coatings you can go over it with.
You need to talk with the technical folk, not the sales staff - but
they should have hand outs.

Some steel comes coated with a sacrificial coating - but this one
seems to be a bit more elaborate.
You still left out to many points - you have to do more homework.




--


================================================== =====
PAUL OMAN ----- Progressive Epoxy Polymers, Inc.
Frog Pond Hollow - 48 Wildwood Dr - Pittsfield NH 03263
603-435-7199 FAX 603-435-7182 VISA/MC/Discover
http://www.epoxyproducts.com
Boating site: http://www.epoxyproducts.com/marine.html
================================================== ======

Paul, Fred and Bioengineer,
Many thanks for your very informative answers. I'm getting a much
better overall picture. I'll come back when I've investigated the
matter more thoroughly.
Regards,
Jesús

It seems Dupont made an epoxy chromate primer (Corlar maybe ??). I had it on a
spec once for an acid tank & it was very tough & stuck to anything. It was an
industrial coating.
Greg Sefton