Thread: Advice on painting my tinnie

Hi Aza
I know nothing about prep for painting "metal" boats but I can pass on some information on Aquacote.
The Bote Cote buiding manual says " Aquacote High Build Undercoat is a two pack epoxy coating which can be applied to sufficient thickness to enable the surface to be faired and smoothed to a fine professional finish in a simple preparation step. Undercoat must be built up in several coats to the required thickness, at a coverage of 3-5 sq m per litre per coat, using brush, roller or spray. We recommend spraying unthinned using a gravity feed gun. Allow a full 24 hours at temperatures above 20 deg C fo the Aquacote Undercoat to cure fully to a hard sanding finish."
Normal painting practice would be to prime the entire hull and then apply various top coats/colours with masking where necessary.

Hey aza,

I wouldn't gin around bogging screw holes, get them welded up, then if you bump something they wont fall out, someone with a portable Tig setup could do it at your place or chuck it on the trailer and take it to them. If the profile on the sanding job is good enough the High Build should hang on but you may need an etch primer on the ally.

HazzaB

Azza,

!. Any area where you weld alloy becomes a hard spot

2 YES you need to etch prime FIRST, before using an undercoat(even EPOXY)

3 RE sand hull and etch prime immediately, Alloy oxidizes within minuets of exposure to the air, so the hull has a layer of oxide now .

4 remember that alloy stretches but does not shrink.

5 after you sand & etch prime , undercoat, rub back & topcoat.

just my thoughts,

Jeff

cheers for the input guys.

so, tig weld
re sand hull
etch primer (quickly after sand)
undercoat (no rush)
top coat (no rush)

3 RE sand hull and etch prime immediately. Alloy oxidizes within minuets of exposure to the air, so the hull has a layer of oxide now . so ur saying my boat has a layer of oxide on it now which i need to get rid of and etch it before it comes back. how long exaclty? by the time i finish sanding it would be like half an hour at best before i get the first bit of etch on where i started sanding

4 remember that alloy stretches but does not shrink. i thought 'alloy' was a compound of different metals. is my hull an alloy?

With epoxy primers, you don't need to use an etch, if the metal has just been sanded and tacked clean. On the other hand a etch will work as well. The moment you sand aluminum, it begins to oxidize. The longer the time between sanding and painting, the more oxidization you'll have. Technically, you get a high amount initially, but this slows to near nothing after the surface has a sufficient film of oxide, to prevent moisture vapor from causing continued reaction.

Yep, the boat you have, in fact most common aluminum are alloys, just as you've described, a combination of materials. Marine alloys are typically aluminum/magnesium often with silicon. The 7,000 series introduces zinc to the mix, but isn't as often seen, particularly compared to the 5,000 and 6,000 series alloys in the marine environment.

Azza,

Aluminum for marine use is alloyed with other metals, .

1/2 hour is no worry , when painting, , .

Aluminum as a metal will and does stretch, and unlike steel it cannot be shrunk, hence if you have a ding /dent you can fill it and fair it or just paint over it, your choice.

Jeff

no worries, just one more question and ill have everything i need to start on saturday.

when i sand the hull before etch priming, what grit would you recommend and how thorough does it need to be? keeping in mind hes sanded it back a fair bit already, looks like he used a orbital or maybe even a grinder with wire brush wheel. so im really just sanding the layer of oxide off.

and after sanding do i need to clean with metho or something else, let it dry and then etch it or just etch straight after sanding?

Thanks for everything

AZZA,

If the hull is already clean of paint , then sand with 180/ 240 Grit use a tack cloth to clean off , you could wipe with METHO as an alternate and no need to dry as METHO should flash dry.

Jeff

I agree, you don't need much more then 180 to 220 grit. With a few layers of primer, blocking and top coat, these will easily fill. I'd use a slightly faster flashing solvent wipe than spirits, such as denatured or isopropyl alcohol. Both will flash faster and leave no residue. I'm not sure of the quality of spirits down there, but in the USA we have two types and the cheaper version will leave a residue, which isn't so with the alcohols.

If it was me, I'd be priming as the solvent flashed, maybe a two person job, making for a really clean bond with the aluminum. Try to work on a very low humidity day too.

There you go Aza - dip your toe into the water of this Forum and before you know it your up to your waist in good information !!!

its definitely helped alot! ill post some before n after pics if she turns out any good hehe

Post pictures regardless of outcome. We all learn from either situation.

heres the old girl



alright so heres a few pics, i have put the etch primer and 2 coats of hi build primer on, will let that set and then put another layer of primer on. i was under the impression that hi build would build up alot more than it did, theres alot of scratches that it didnt fill but hey its an old tinny, not gonna be perfect.

the problem with painting outdoors is relying on the weather and the bugs.. they were attracted to the bright white, i had about 10 on there that got stuck and started moving around trying to get free while screwin up the paint. might try moving it off the grass onto the pebbles next time.

as you can see there was a bit more paint on the boat than i originally thought, we tried to save some money by getting the paint off ourselves, we stuffed around for 2 days with paint stripper and a pressure cleaner and didnt get very far so ended up getting it sandblasted. it was like new! this is a must for anyone considering to restore a tinny. it made the ally nice and coarse, the paint should stick no worries

before blasting, slaving away



after blasting. i asked him to keep it at $300 so he did a straight forward job. one guy quoted $650! still a few small areas that need sanding but he got all the paint off thank god!


so it sat around after being blasted for about 4 days then i cleaned it with 'alibrite', awsome product. got it from BCF. ally was clean as but i used it to remove any oxide film. pressure cleaned that off and then went to wipe it down with a rag and metho but found that the metho was actually leaving residue on the surface. i think the boat was clean enough so i didnt apply anymore. see pic

its completely dry but just has some discolouration. maybe the metho wasnt the best quality. just got it from bunnings...



then the etch was applied, pretty straight forward, ive never painted like this before so i hope i havent done it to thick or thin... i think it cam up alright.





i applied a thin coat of high build bout 30mins after and then went straight over that with quite a thick coating. now she is drying.





when the weather is good (bloody canberra) i will give it a light sand and finish the undercoat then proceed with colours.

seeing as this thread is mainly about how to stick the paint to the ally i wont post any updates throughout the job, but i will show u the finished product in a couple of months.

guess we wont know if this method works untill the paint proves itself after a couple months but after all the research and prep that ive done i am pretty confident.

the etch used was ppg cobra 2kcf and cobra 2kcf catalyst. i used about 1600ml in total.

primer was aquacote 2 pak hi build epoxy primer. used alot of that, i will probably have used the full 4 litres after another generous coat. then i still have the top and inside to do

feel free to ask any questions

AZZA,

Before you hit it with the next coat of undercoat , give the hull a light sand , as the paint will have hardened and the next coat will need a mechanical key to hold .

This will also help those deep scratches to disappear a little more..

the hull is looking good , from what I can see, the pic's come out a little small to pick up detail.

good luck with the weather , you will live in Canberra.

Jeff