GulfCoastPaint MCU--100 PRIMER/FINISH is its other name. It's been discovered by many
skippers, primarily because it is available in quart cans from epoxyproducts.com. Some of
mine here, it is an extraordinary coating, very different from any other we use around the
boat, requiring imco an application learning curve (see post 424 for some surprises.)
It is an industrial paint so maybe we can expect excellent longevity and weatherability.
Aluthane coating is both finish and primer -- perhaps the manufacturer is not entirely sure
what this coating can do. You can print out a two page 'brochure' from their site, 1/2 of
which are photos of gigantic industrial plants. But it's already obvious that this coating is
a marvel, a big deal, and yet to find its full potential. I picked up a readable inhouse safety
data sheet off pauloman's epoxyproducts site (but don't know how.) It is here we find the
three (there may be more, Stirling seems to have one like this) commercial names for this
aluminum paint revealed: Gulfthane, MCU-100 Primer/Finish, and ALUTHANE.
It's gotten around in other circles...
PRODUCT DESCRIPTION
"A one component, Moisture Curved Polyurethane Aluminum Coating. Has excellent
adhesion to sound, tightly adherent rusty steel, and other marginally prepared surfaces.
This low viscosity, high 'wetting' coating undergoes a rapid molecular weight change as it
polymerizes into a high molecular weight finish which provides excellent corrosion and
abrasion resistance. Its resistance to creeping, undercutting, and blistering is superior to
epoxy primers. MCU-100 is also a barrier primer or tie coat to prevent lifting of strong
solvent top coats over conventional coatings, and most chemical coatings.
PRODUCT FEATURES
1. Primer for all types of surfaces.
2. Excellent 'wetting out' properties over sound, rusty steel.
3. Fast recoating, 1-2hrs.
4. Cures down to 18F on dry surfaces.
5. Excellent corrosion resistance, passed 1,200 hours in salt cabinet.
6. One package. Easy to use
7. Outstanding abrasion resistance
8. May be topcoated with most generic type coatings
9. Very good weather resistance.
10. High heat, up to 400F dry.
11. Excellent as a barrier coat over lead based coatings."
SINCE WHEN ARE URETHANES CONSIDERED PRIMERS ?
This should open up possibilities for any doubter. As a 'primer', still not sure about how
one goes about adding a series of 'generic' coats to polyurethane... which I always
assumed was the final sweat achievement . Peculiarly, this kind of utilitarian MCU rolls
on very very thin like LPU, but isn't bling. NO mention of above/below waterlines.
Abrasion resistance may suggest rubbing down with nylon/grit pad. *
TECH DATA for thinner is an inhouse 'SA-50'. MSDS reveals xylene is a major ingredient.
Certainly didn't need thinner when doing the mast. Most sustained use I've had with it.
Now, prime use for this urethane has been for dressing corroded steel pilings in water.
Do we assume salt water? Which as we know can entirely erase steel from the planet.
In coating our boats we are always aware what primers are OK below the waterline.
There is no caution that this primer cannot be used underwater. No words to that
effect. Many a neglected aluminum skiff has been born again with a single coat of
Aluthane. (Later EDIT: Just talked with manufacture's rep at GulfCoastPaintMfg, the
makers of MCU-100 (Aluthane). He didn't know why we cannot use urethane paint
underwater. He did say that any urethane, including LPU, can be topcoated with any
other paint system. Therefor you can say, it's a 'primer'. However, he would not advise
using Aluthane as a primer on the bottom of a boat, even if topcoated with a twopart
epoxy OR a hard bottom paint... but didn't know WHY? Don't like this kind of mystery.)
If you like a galvanize look, this coating will look exactly as you rolled it on 10 years
later. Don't know that totally for fact: took a couple rusty hardware store thin sheet
metal horses, the kind that start rusting out the door... had some Aluthane left over,
hurriedly rolled it over dirt, dust, rust, bird droppings and spider webs. Transformation
is still a minor miracle: bird droppings still encapsulated, and today, years later, they
look just painted. Amazing to me is that an aluminum filled paint is used directly over
and within the rough rust on steel -- and yet doesn't create a battery... these two are
in no way close friends around the galvanic table.
Assumed that polyurethanes are always two part. Here we see one-pot referred to
as 'poly'. On a molecular level urethanes are films made of polymers fused together at
highly reactive poly-isocyanate sites, forming strong bonds known as chains.
Moisture causes the reaction that creates amines which combine with isocyanates that
cure into urea that bonds chains together The process releases CO2. Isocyanates are
hazardous organic compounds of 'functional' (reactive) groups of molecules that inter-
react with other groups to form a specific chemical --a simultaneous phenomenon
called 'hydrogen bonding' occurs between the chains of molecules that further increases
film strength -- as we see in the list of attributes above. Pretty amazing stuff, but this
says this one-part aluminum filled primer CURES rather than dries like regular 1-part.
Who's going to try it as a tiecoat primer. "metalfilled paint PRIMER? You're kidding."
Begs the question: why can't polyurethanes be used underwater? "They cannot."
{google ignores answering that one!!!} Why not amazing Aluthane? Assume, with
continuous immersion in salt water, coating dissolves. What's with this chemistry?)
There are many thermoplastic polyurethane elastomers, plastic rubber, goops, caulks,
sealants, adhesives, tank linings and dips - some filled with glass spheres or fiberglass
- that can be used underwater. These are the only p.urethanes that can be designed
for total immersion use. None of these rubbers are hard coatings.
Seems, ebb has learned one thing... Alutane is devitalized with a certain chemical
paint stripper. The thin tough multicoat didn't die without a fight, came off with putty
knives and carbide scrappers in obstinate strips. We'll use it again -- with a new green
pre-prep called PreKote* which replaces the toxic heavy metal acid & alkaline
conversion washes -- And this time it'll be the FINISH coat!! Love that galvanize look!
*from AircraftSpruce. PreKote SP is a trademark of Pantheon, an aerospace tech.
It provides this interesting solution that produces "a polar/non-polar molecule that
attaches itself to permanently embedded contamination and attracts the {next} coating.
In contrast, traditional conversion coatings containing heavy metals such as chrome or
zinc have no mechanism by which to attach themselves to permanently embedded
contamination, resulting in coating failures such as blisters and outgassing (pinholes)."
Again, using aluminum filled LabMetal on the mast, and hope that this PreKote
treatment will give due consideration to my contribution of filler & fairing bonded
'contamination' on the aluminum metal mast, and myriad 50 year old embedded oxide
defects. PreKote SP is not a toxic conversion coating, and does not permanently
change the metal surface... it is an integral part of a coating system. It must be
overcoated. And I hope it strongly embraces my coating choice, Aluthane! As far as
exposure to solvents, carcinogenetic toxics and contaminated water runoff goes, this
pre-treatment is a huge responsible step toward greener painting of aluminum ( and
a number of other metals and surfaces). Been around for two decades... wish I'd
read up on it before I chose to use the insane chromated stuff!! Tested by DOD
and the USAirForce, given their blessing. No idea what film chemistry PreKote uses.
Read every word I can find on what Pantheon Enterprises says about their PreKote.
Can't find a single word for its use under water, or total immersion. They do not say,
Do not use Prekote underwater. Don't use it when painting your submarine.
(Interlux has a very different hibuild, above-waterline, sanding primer called Pre-Kote.
It does not carry a registered trademark)... imco. www.pantheonchemical.com
EXACTLY WHICH SCOTCHBRITE PAD?
The whole reason for using a pre-prep on aluminum is to remove all traces of oxide
and other contaminates. PreKote as an alternative to acid/alkaline heavy metal wash
is a godsend, if it works (haven't used it yet). It has a very specific method for
application that involves scrubbing the aluminum surface with a specific nylon pad.
Instructions given for using PreKote on your aeroplane are in military specs. But
there's a footnote stating MAROON 3M scotchbrite aluminum grit nylon pads
may be used. BUT cautions to use no other brand. Instructions are so specific:
ONLY the maroon 7447 scotchbrite pad may be used, NO other pad color either!!
Other pads may leave behind oil, soap, rubber or the wrong grit in your substrate.
A little pop to retain... for all other surface preps... for any coating. MAROON !
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~
"I woke up after a night's sleep to the tune of a robin on the windowsill. I realized it
was Spring. It was time for Marlow to take a long easy weekend some place... some
place where surf meets sand." Raymond Chandler, The Last Laugh, OldTimeRadio
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