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Old 08-02-2017, 06:40 PM   #1
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Grinding/finishing Aluminum

As you know, Gwaii Haanas is aluminum. LIke many boats that worked for a living, it has had a hard life. I have no intentions of gilding this rather tatty lily but I would like to clean up the deck. It has had various non-skid treatment over the years and I have nearly got the worst off but I would like it to be uniform and non-skid. Blasting of some kind appeals but it has become very difficult to do (unless I take a compressor on board and find a nice anchorage and do it "out there.") at shipyards. I considered using a 7" rat-tail grinder with a flap wheel, that is still my preferred, it leaves an interesting industrial pattern and a surface not too slick for bare feet (salt-wet aluminum and bare feet is as lethal as Crocs on wet kitchen floor).

Has anyone finished aluminim decks or anything similar? Paint fails and the aluminum corrodes underneath it. Those sticky sandpaper sheets also corrode the aluminum.

I suppose I could paint a non-skid on it and hope it lasts longer than I will.

Any great ideas?
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Old 08-02-2017, 07:40 PM   #2
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I painted my fiberglass decks with Kiwigrip. It is excellent for non skid and very easy to apply. Not sure how exactly you would need to prep the aluminum deck first.
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Old 08-03-2017, 08:04 AM   #3
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The very coarse material pad (like scotch brite but aggressive!) and a floor buffer/polisher might work, and not remove much but the old finishes.
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Old 08-03-2017, 09:29 AM   #4
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When you grind/sand aluminum an oxidized protective coating gets removed dosn't it? And once you paint you'll be painting forever. The huge reason people buy aluminum boats is so they don't have to paint.

When I build/fabricate something out of aluminum I frequently sand the flat surfaces w my belt sander. Like the unform sanded look.

Xsbank, what do builders do? Go to boatdesign.net and look in the metal boatbuilding forums. I'm sure what you seek is there to find.
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Old 08-03-2017, 09:53 AM   #5
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To slightly hijack here, but it is about removing finishes from aluminum...I have a Scanstrut Tapered Radar Mast that is shedding it's powder coating in some places and holding tight in others. The mast has wings and holds my closed array radar and my KVH antenna. I got a quote to remove all the finish and repaint, in situ, for $800.

Does this sound right for a professional job? The guy has 40 years experience as a painter in the marine industry, mostly the yards in Ft. Lauderdale.
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Old 08-03-2017, 03:19 PM   #6
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There are different sand papers that are made for specific material. IE: stainless, aluminum, steel. Each paper has properties that support the selected material. If you use sand paper discs for AL you won't get the oxidation and contamination.
Go to the 3M website they typically have information on selecting the right stuff
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Old 08-03-2017, 05:42 PM   #7
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No luck on boatdesign but EagleCraft uses Alwgrip paint. Not an option for me, needs to be ground to bare metal, acid primed and painted with a sprayer. NBL. I have too much deck.
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Old 08-03-2017, 05:59 PM   #8
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I have no experience in aluminium at all so pardon me if I write some enormous idiotic things.
Wouldn't it possible to use some paint or varnish (whatever it is would stick to aluminium) mixed with sand for the non skid effect? While not specific to marine use there are some paint specific to aluminium used on car/windows/whatever is made of alu.
Than for old paint striping, would water pressure be something to check? Some high pressure jet are able to remove pretty anything and would be far less dusty than sand blasting.
I write this I say nothing, just some thought from the top of my sick head

L.
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Old 08-03-2017, 07:11 PM   #9
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Similar situation as yours with an aluminum deck. The alwgrip route is not possible at the moment as the prep is huge with a cost to go with it. Ended up using home depot outdoor paint, the outdoor patio and primer stuff. Felt like a redneck at the time, but it actually works well and lasts a couple seasons in the pnw
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Old 08-03-2017, 09:31 PM   #10
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Quote:
Originally Posted by Xsbank View Post
No luck on boatdesign but EagleCraft uses Alwgrip paint. Not an option for me, needs to be ground to bare metal, acid primed and painted with a sprayer. NBL. I have too much deck.
Nothing to add regarding the aluminum deck, however I saw your boat a few days ago in Gorge Harbour and I came around in my all aluminum, non-deflatable inflatable hoping to see a guy matching your avatar pic but didn't see anyone around. Sure I will bump in to you again some other time for an introduction. Your flap disc idea may just give it the "sharkskin" effect you desire.
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Old 08-03-2017, 10:02 PM   #11
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Making aluminum non-slip

I worked on a custom built mud racer years ago. The body and floor boards were unpainted 5052 aluminum for corrosion resistance. Our driver complained about how slippery the floor was. The answer we came up with was 36 grit aluminum oxide sanding disk on a DA air sander. The aluminum oxide did not leave any trace metals to discolor the finish and the circular dual action pattern made an excellent non-slip. No more driver complaints and easy to clean.
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Old 08-03-2017, 11:06 PM   #12
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Not sure what a mud racer is but the solution sounds great! I am going to load up with aluminum abrasives and try it with my 4 1/2" grinder to see what I can see (and to see if my knees will survive it).

Nightsky, I'm sorry I missed you, I was tricked out of Roscoe Bay into Gorge Harbour by some "Little Bo Peeps" (little-boat people) and forced to partake in an expensive, adequate (but pleasant) dinner in the restaurant. A much better meal is to be had at the Laughing Oyster! My new anchor works a treat, I usually plow up the bottom in Gorge as if I planned to plant corn, but this shiny one is so much better, getting a set and not trying to cling to that rock in the middle (NOT AN ANCHOR THREAD) that I didn't worry about staying a night there for a change. We are out again when the dogsitter gets back in a week or so, so will look out for you.

Michaeln, I am keeping paint in the background for now, somebody had used something similar in the past on some parts (painting right over the sticky non-skid pads, which makes it look like crap) and like the idea of the Home Depot stuff. I put some of that down on the engine room floorboards and it took a week to cure, just plain old paint. The enviro-weinies have spoiled paint, it doesn't stick to anything any more and its so thin you need three or more coats. I primed my galley cupboards and sanded them and it still took three coats and some touchup to cover the old gruesome panels.
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Old 08-03-2017, 11:37 PM   #13
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The idea with the dual action sander is that the sanding disk lays flat on the surface creating an orbital swirl. If you don't have air readily available, there are cheap electric dual action sanders available (Home Depot) that can take aluminum oxide sheets cut to size. (I do not know if sheets come in 36 grit or not) The non-slip part is from the random heavy scratches the course grit leaves. If you use a purely circular grinder with coarse grit, it will remove a lot of material, fast!!
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Old 08-04-2017, 05:16 AM   #14
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"The enviro-weinies have spoiled paint, it doesn't stick to anything any more and its so thin you need three or more coats."

Perhaps , but the Rustoleum folks have a great aluminum primer that works well in a single coat.

Unlike most primers it looks good after a year , with no top coat, in FL sunshine.

It also is the only way to paint galvanizing , and have the paint stick.
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Old 08-04-2017, 08:16 AM   #15
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Re: grinding aluminum; use the discs made for the purpose. Discs made for steel will fill quickly and become useless.

Re: sanding aluminum; use the discs/papers made for the purpose. Discs/papers made for steel, paint and wood will fill quickly and become useless. Sanding with wet-or-dry papers, used wet, will do OK.

Re: removing the oxide layer and exposing the aluminum to early corrosion; the oxide layer re-forms all but instantly. That's what makes the stuff harder to paint and weld.

Re: leaving an attractive bare aluminum surface; use an orbital sander and you'll get nice little circles which appear as a specular finish from just a little distance.

Re: painting / spot painting aluminum. Interlux makes Procon primer intended for underwater use. They tell you to not use it above water. I did; it works fine. I spot primed my corroding aluminum sailboat mast over a decade ago. I overpainted with Brightside Polyurethane. It still looks fine and there is no / very little creeping corrosion (out from under fittings) anywhere.
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Old 08-04-2017, 09:38 AM   #16
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Painting aluminum that is not new is always a crapshoot b/c tiny pockets of corrosion fester and enlarge under the paint. You can't really get good zinc-chromate primer any more at retail either. Putting a nonskid directly onto/into the deck with a grinder sounds foolproof altho it too will corrode in time. I would email a couple of deck coat manufacturers (Evercoat & Kiwigrip come to mind) asking about prep, priming and adhesion to aluminum, ask for samples. Use only products that are meant for aluminum as mentioned repeatedly above is good advice. Sand, acid wash, prime in small sections.
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Old 08-07-2017, 08:49 AM   #17
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Having worked in the metal fab industry many years ago, I had used a pneumatic needle gun for descaling. It would leave a dimpled surface in aluminum .
Google "pneumatic needle gun".
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Old 08-07-2017, 10:19 AM   #18
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Good morning. Thank you, I did Google a needle scaler but its tiny, I think in round numbers I have about 780 square feet of deck to do, less the wheelhouse roof and some of the foredeck due to reflexions.

I tried an orbital sander with 60 grit (all they make for an or orbital) and it is not nearly aggressive enough and makes a polished surface. Very slow. I think if its a tool it will have to be a grinder with some kind of 36 grit or an actual grinder. After today, the place stops being a resort and I can go go back to making boat noises in a marina so I will test the grinder and my knees.

I think I should rent a compressor and a gun and go and anchor out and sandblast the boat.
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Old 08-08-2017, 06:03 AM   #19
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"it will have to be a grinder with some kind of 36 grit or an actual grinder"

The floor sanding folks have 36 and 24 grit silicone carbide that is easy to stick to a thick sanding pad with sanding disc adhesive.

Cut it square the corners will help in not digging into the deck.

FAST ! but use with great care.

Paint remover is also made for aluminum .
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Old 08-20-2017, 05:28 PM   #20
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Quote:
Originally Posted by Alabama Boater View Post
I worked on a custom built mud racer years ago. The body and floor boards were unpainted 5052 aluminum for corrosion resistance. Our driver complained about how slippery the floor was. The answer we came up with was 36 grit aluminum oxide sanding disk on a DA air sander. The aluminum oxide did not leave any trace metals to discolor the finish and the circular dual action pattern made an excellent non-slip. No more driver complaints and easy to clean.

You bought up an important point with your 5052. Aluminum comes in an array of alloys, some withstand things such as a salt environment where others surface chalk and pit. So don't be surprised what aluminum will do especially when the type of aluminum is unknown
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