Painting Various Bits of Aluminium Questions

[savageseadog]

I need to paint my spreaders which are a black anodised aluminium which has deteriorated to the point of a little corrosion in places where there's been abrasion

I also need to paint a mast step which is a casting which has electrolysed pitting. Was originally a black passivated finish of some kind possibly some kind anodising similar to the bits used on aluminium mast fittings.

What kind of paint treatment and finish do the forum recommend please?

 

[Stemar]

I won't pretend to any expertise, but I refurbished some badly corroded window frames with plastic metal to fill the holes followed by a couple of coats of Hammerite primer for non-ferrous metals and a couple of coats of smoothrite. 3 years on they're fine.

 

[vyv_cox]

Non-ferrous metals need an etch primer which is alkali based. Hammerite do one that has worked for me on aluminium and on my galvanised garage doors. My radar scanner sits on an aluminium adapter plate that was etched and painted with Hammerite products. That was almost 10 years ago and it is still excellent. Some forumites suggest that Hammerite is no longer the product it was so you may prefer another top coat but the primer still seems good.

 

[Bosun Higgs]

I once stripped and painted a previously black mast - I couldnt stand the look of it, rather like flares, long hair and the droopy moustache!

To strip off the anodising ( better adhesion plus if you leave the black there and chip the paint ..... ) I used a hot caustic soda solution with all the safety kit since it will literally dissolve you if you get it on bare skin. Good way of disposing of a body if you ever have to.

I digress. After that step, I sanded the mast fairly coarsely ( 80 grit) and then used an etch primer from epiphanes. Undercoat was sprayed on epoxy ( industrial paint supplier used for painting steel frames for buildings) with a couple of top coats of twin pack poly ( same source). Accidentally sprayed the yacht club windows but thats a different story.

Worked like a dream and had the great side effect that the sail slides slid up the mast like a well greased pole dancer.

 

[srp]

I use zinc chromate primer (after a clean with hot caustic soda solution), from http://www.lasaero.com/site/products/article?id=G03H0GVF9.

You need a mask and all the other sensible precautions when using stuff like this. A normal car spray paint will give a decent top coat. I did my spreaders and furling gear about 4 years ago with this primer and a can of metallic silver wheel paint and they still look as though they were done yesterday.

 

[CelebrityScandel]

An etch primer has for a long time been the recommended first coat on aluminium

International seem to have discontinued their Etch primer .

I think you may mean that "An etch primer has for a long time NOT been the recommended first coat on aluminium". That may be the likely reason, if as you claim (I have not checked), International have discontinued their etch primer.

As far as I know all major paint manufacturers' specifications for aluminium (and steel too) marine vessel application have been for many years now epoxy primer straight onto abraded aluminium.

If people wish to get some modern product application advice a check of the specifications of the major paint manufacturers will do that for them. For example, the International "Boat Painting Guide" says -

Aluminium
Degrease with solvent or Super Cleaner. Sand well
using 60-120 grade (aluminium compatible) paper.
Clean thoroughly and allow to dry. Prime using an
International primer as soon as possible (within
8 hours) following the product recommendations
provided in the paint systems guides.

We have much more aluminium than most here and that is how ours was done, it has also been standard industry practice for at least a decade now.

 

[BAtoo]

I need to paint my spreaders which are a black anodised aluminium which has deteriorated to the point of a little corrosion in places where there's been abrasion

I also need to paint a mast step which is a casting which has electrolysed pitting. Was originally a black passivated finish of some kind possibly some kind anodising similar to the bits used on aluminium mast fittings.

What kind of paint treatment and finish do the forum recommend please?

As others have said - Hammerite Etch primer for Ally, then smooth topcoat.

Works well.

Above all - simple.

 

[CelebrityScandel]

"if as you claim (I have not checked), International have discontinued their etch primer."

WTH is that supposed to mean. It has been discontiued !! Although a similar product is still available in the USA.

Hi VicS - As I said I don't know if it has been discontinued or not as I have not had any reason to check.

Etch primer for marine service has not been recommended for many years now for aluminium by the main manufacturers of marine coatings so I have had no reason to see if it is still available. As I said, they all (I know of no exceptions for painting vessels and the 3 manufacturers we have used over the last decade have all been the same) specify abrade and prime with their epoxy primer. So if International have discontinued their etch primer as you suggested I was just suggesting that may be because they no longer include it in any of their painting specifications so have no need to manufacture it anymore.

Hammerite is a decorative finish and while I know some use decorative finishes to paint their boats it is not the best servicable solution. However, as far as I am concerned people can paint their boats with whatever they like, I was just pointing out what the current best and professional practice is. We are in the situation where our investment in the boat is such that is the only approach we can sensibly take but I understand that others may be in different situations where it does not matter so much to them.

 

[savageseadog]

What about Chromate primers?

 

[Strathglass]

I painted my spinny boom.

First SPRAYED with etch primer (epiphanes). Then sprayed with grey International Perfection two part paint (with the appriate thinners).

If the primers is not sprayed on it is almost impossible to get a good finish as it cannot be sanded.

No scrapes, chips or pealing off in two years use.

I have painted several booms in the past using the same method all without any problems.

Iain

 

[Bosun Higgs]

The idea of an etch primer was to etch the surface and give the paint something to adhere to. Anodised ally is polished smooth before anodising so it is very non grippy. Either etch or abrade or both before painting.

Then you need to make sure that coverage is 100%. Problem with paint on ally is that as the ally at the paint edge oxidises, it travels under the paint and starts to lift it. Thats why Ovni boats have a plastic tape covering the bare ally / painted ally join