by Bob Norson
I know the quote above well because it
is mine. It reflects one of the cruel lessons one learns from
painting on a steel boat. Another one is; the first step
is the most critical one with each subsequent step decreasing
in importance. Both quotes being paradoxically true but the later
doesnt sound as sexy.
Lets start with a few things I know that
dont work; Paint right over Rust! or Kill
Rust. You find these things in the local hardware store.
The clerk will swear by the stuff. Maybe for temporary coverage
of a garden mower but dont waste your time on a boat...
Another? Rust Converting Paint! or just rust converter.
Not up to the job. Iron oxide, rust, is changed chemically when
exposed to an acid, becoming iron again. Rust converter is merely
a dilute acid and the paints incorporate some of the acid into
the mix. Maybe OK for detail work on your old car... I tried
one of the best of the breed, Ironise by Gal-Mat
and wound up re-doing all the area I applied it to. I did keep
it around for spot repair because it is so easy to apply, being
water based, and quickly re-coatable.
In short, a steel boat in a salt water
environment is the most severe test of a coating system. If you
can blast the steel with abrasives the solutions are far easier.
Go right to the best quality epoxy primer and carry on from there.
The green police are making it harder to find a place where you
can blast and places where you can are quite expensive due to
the regulations. So as a practical matter, knowing how to get
a reliable paint system repair on weathered steel is a necessity
for steel boat ownership.
the Preparation Stupid!
Being the proud owner of one of the ugliest
box trailers in existence, I found a suitable piece of weathered
steel to demonstrate on right in the back yard. (lucky me!) As
you can see by the photos, a nice deep scale rusted mess similar
to what you find on a neglected steely. The old fashioned hammer
and chisel is a good place to start (air powered chisel even
better) but be careful of deceit at every step. There is no way
a chisel will remove rust suitable for painting. The next step
for non-power assisted tools is the screw driver tip scraped
vigorously across the area. Better, but not half way there yet.
You can succeed in this fashion on small areas but it takes particular
attention to minute detail and way more muscle than you would
imagine. If you have magnification available, this is a good
time to use it. Every step up in magnification unfailingly reveals
a bit or more of scale that missed your attention without it.
When you THINK you have it conquered, go over the area firmly
with a steel brush and have another look. I bet you find more
but should you judge the effort worthy, you are ready to paint,
insuring your surface is dry as well as clean.
If you are in an area that will allow for
the noise an air compressor of reasonable output (10 cfm minimum,
15 better) a scaler tool is more effective and much easier to
DO NOT FORGET EAR AND EYE PROTECTION! Go
ahead.. ask me how I know but talk really loud, OK!
The makers of the tool generally recommend
about 40-60 lbs line pressure to run but I find they hardly work
at that pressure. I got away with 80+ but any more and the tool
doesnt last long. The tool makers also recommend a daily
oiling of the tool. Be careful of this as any excess oil is blown
out the front of the tool and the oil spots will stuff your paint
job. If you know or suspect this has happened, carefully wipe
your repair area with methylated spirits to remove the oil contamination.
This may be a good idea in any case as the alcohol will tend
to remove moisture as well. But Im getting ahead of myself.
Psychologically it can be hard to persevere
because you dont want to believe it is as bad as it is..
but dont be fooled.
One of the hardest parts of this is to
train yourself to recognise the scale. In photos at bottom, is
a spot I missed. I did pick it up when I put the first coat of
paint on. I saw the small lump. It was when I put these photos
up on the screen that it became more noticeable. With my experience
I should have caught it sooner but it appears (sorry) Im
The lesson learned is you just cant
over-do the preparation. No paint product will save you from
scaled rust. It will come back to haunt you. If I am successful
in getting this point alone across to you its a win. So..
when you have done it to completion the forth or fith time and
finally no new tiny bit of scale explodes in dust from the tool,
its time to go over it with the steel brush then a thorough
clean and dry. Use acetone to wash if you think it is possible
the surface could have some oily contamination... or just because.
It never hurts.
Apply your pre-prime paint. There are only
two paints that I have tested to satisfaction. POR 15 is suitable
for spot repairs due to its fast recoat time. For larger areas
where it pays to invest the time, Altex pre-prime 167 is the
champ. It goes on piss thin and encapsulates surface rust and
even light scale rust. The 167 has a long dry time, 6 - 8 hours
and likes to be recoated when it is slightly tacky to the touch
This applies to all the paints you use.
If clear instructions on preparation and use, re-coating times
etc, are not on the container then your paint dealer will have
the specs on file and will be able to supply you with a copy.
Poor prep and failure to follow instructions are the cause of
99% of paint failures.
POR 15 is strange stuff. Get the smallest
size container you think you can get away with. The stuff drys
so hard that if you get a small amount on the lip of the tin
you will have to cut the thing apart to get it open next use.
So never paint directly from the container unless you figure
its a throw away when done. I use disposable plastic spoons
for dipping paint out of a container and also for measuring small
amounts when using two pot paints. A handy tip for the POR 15
is to use a layer of plastic wrap under the lid when you put
away. That way if there is a small spot on the lid you might
be able to open it next time anyway.
YOUR JOB TO ACCOMODATE YOUR PAINT SYSTEM
I like to manipulate the repair so that
by late morning the repair area is ready for paint. Put on your
first coat of POR 15 and stand by. Especially in summer it can
go quick and you dont want it to go hard. Put on your second
coat when there is still a little tackiness to the
surface, two hours+ or-. Two coats minimum and three is better.
If all goes well you may be able to get the first coat of epoxy
primer on and have it skin out before the evening
dew. My preference for epoxy primer is Wattyl PR250 because it
is cheap and good, a rare combination.
I prefer to paint on the 167 in the afternoon.
If the steel develops a little rust "blush" from an
overnight dew on the first coat of 167, no worries, paint your
second coat right over it, then you should be ready for epoxy
by midday or early afternoon.
Especially if you are working on a flat
surface you may want to fair the repair. With the first coast
of epoxy primer in place its a good time to do it. Wattyl
Fairing Compound is my favourite. [ this product had been discontinued,
use instead epoxy resin with filler such as phenolic microballons]
It goes on smooth and resists air bubbles in the mix and it sands
so easy... as long as you dont let it wait too long. I
tried the Jotun stuff as well but I found it harder to work and
prone to the bubbles. For application the best tool I found is
a grout spreader for doing tile work. Its hard rubber blade
and wide edge are perfect for the job, just filling the low spots
without piling it on everywhere. They are a $5 tool most places.
A wide putty knife doesnt do as good a job.
After the fairing compound put on your
first coat of epoxy undercoat There are many good high build
epoxy undercoats. Check local supply and compare costs but Ive
never gone wrong with the Wattyl. At least two coats of undercoat
over the fairing. (As applied by brush) As far as top coat, I
have over 12 years experience with Wattyl Poly-U-400 and it has
been remarkably tough and has the advantage of being easy to
re-coat whilst other types of polyurethane have to be sanded
or chemically treated to re-coat once cured. At least two coats
of top coat as well. Thats 7 coats minimum.
Whitsunday Ocean Services of Airlie Beach
is the source for the paints used in this article.
Contact them here.
And am I qualified to instruct on this
Well have a look here
and judge for yourself..