Suitable primer for painting aluminium?

[Nick TParticipant @nickt]

Hi All,

I am restoring an old Elliott pillar drill using grey primer and machinery paint bought from Stationary Engine Parts. I am using some sheet aluminium and a die cast box to hold new controls and don't really want to buy aluminium primer if I can help it.

would I be OK with grey primer if I give the aluminium a good roughing up with a wire brush first?

Many thanks,

Nick

[Nick TParticipant @nickt]

[donkeyParticipant @donkey]

You really need an etch primer. As the paint will eventually chip and peel off and or bubble without it.

brian

[Bob Brown 1Participant @bobbrown1]

As Brian said the only way to paint aluminium is with acid etch primer with out it the paint will not adhere to aluminium or galvanised steel if it comes to that.

Bob

[Nick TParticipant @nickt]

Thanks for the advice Bob & Brian – much appreciated.

Nick

[“Bill Hancox”Participant @billhancox]

Posted by Bob Brown 1 on 01/11/2014 17:14:18:

As Brian said the only way to paint aluminium is with acid etch primer with out it the paint will not adhere to aluminium or galvanised steel if it comes to that.

Actually, before the advent of pre-painted aluminum sign blanks, I hand lettered and silk screened hundreds of aluminum and galvanized signs using zinc chromate primer. The signs stood up to seasonal weather changes and road blast extremely well. A light fine sanding of the metal is necessary followed by a thorough degreasing. Aluminum must be primed immediately following the preparation before new oxidation begins to form. Also, avoid fingerprints. I do know that the refinishers at the neighboring military helicopter training unit used an acid etch primer on their aircraft. Important to note that my process was not subjected to very high temperatures such as those that occur on engine cowlings..

Cheers

Bill

[ScottParticipant @scott]

We used to use zinc chromate to prime galvanised handrails on ships. Haven't seen it for years

[HomeUseParticipant @homeuse]

Zink Chromate primer is available on EBay and in many D I Y shops – would recommend for use on alloy

[ronan walshParticipant @ronanwalsh98054]

You could use 2 pack epoxy primer, its not a dangerous isocyanate paint, it doesn't need an etch primer , it will stick very well to anything you spray it on, and lastly it is very very tough.

[Gordon WParticipant @gordonw]

Just for interest- Yesterday I pressure washed my home made van, all the paint on the timber peeled off, the paint on the aluminium and steel parts are still good. Timber was primed with the proper, expensive, aluminium based wood primer, the metal work slapped over with Hammerite.

[HopperParticipant @hopper]

Rub the job down with vinegar before applying regular primer. The vinegar etches into the ally so the primer can stick to it.

[frank brownParticipant @frankbrown22225]

I am not sure that vinegar is the correct thing to use, an alkali is better, try washing soda or caustic soda (v. dangerous but effective), then hold in plastic gloved hand to stop finger prints. Hose down with clean water, dry over heat and prime quickly.

Frank

[Ian S CParticipant @iansc]

We used Zinc Chromate primer on all aircraft painting, and most of our aircraft were painted with two part epoxy paint. Ian S C

[NJHParticipant @njh]

I agree with Ian

For some years I had a metal glider – always used Zinc Chromate as a primer on that.

Norman

[Oompa LumpaParticipant @oompalumpa34302]

You are only priming a pillar drill so find your local (proper) autopaint store and they will sell you a small tin of aerosol etch primer. Most all real autobody paint suppliers make up aerosols of almost anything on their premises nowadays.

I do this regularly as it is quick, simple and cost effective.

graham.

[Michael GilliganParticipant @michaelgilligan61133]

It may, or may not, be particularly relevant to painting but I would just mention that Phosphoric Acid [readily available in rust-treatment products like Jenolite] is an excellent etching agent when using epoxy resins on aluminium. … But, having no primer in it, the epoxy needs to be applied very soon after etching [within about 30 seconds if possible].

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Here is the MSDS for Jenolite.

[Nick HughesParticipant @nickhughes97026]

U-POL ACID #8 ETCH PRIMER, available from most Halford stores in the UK:- **LINK**

[Neil WyattModerator @neilwyatt]

I've never been able to find it in stock at Halfords. An availability check said I could 'collect from 1pm Wednesday, Looks like it is an 'on demand' product.

Neil

[Bob Brown 1Participant @bobbrown1]

Zinc chromate is not the safest stuff as it is a known human carcinogen

Bob

[mike TParticipant @miket56243]

Neil

At Halfords the U-POL ACID#8 ETCH PRIMER is not normally on the shelf with the car colour paints. You need to look on the shelf with the specialist spray paints and fibreglass kits.

It is good stuff for steel and aluminium, it also does a very good job with those "difficult" materials such as brass and stainless. Now I have found it I would never consider standard primer again.

Mike

[“Bill Hancox”Participant @billhancox]

Posted by Bob Brown 1 on 03/11/2014 18:42:54:

Zinc chromate is not the safest stuff as it is a known human carcinogen

Bob

Although zinc chromate primer is a hazardous substance that must be handled; stored and used under prescribed conditions, it is not carcinogenic to humans. This Material Safety Data Sheet (MSDS) dated 11/18/2013 is evidence of that. Please see page 1; the paragraph entitled "Carcinogenicity".

**LINK**

Cheers from an old retired occupational health and safety officer.

Bill

[Bob Brown 1Participant @bobbrown1]

The HSE have a different view see **LINK**

[Jerry WrayParticipant @jerrywray14030]

That's a totally different type of primer.

2-pack self etching primer is the sort of primer that performs best on aluminium. The coating to which 'Bill' links does not contain zinc tetroxy chromate (ZTC) which is an essential ingredient and it is this which is the hazardous component.( That's excepting the corrosion hazard of the phosphoric acid contained in the activator component. These primers were developed by the military in WWII based on research which ended up in a formulation which has been in use ever since, but declining.

Follow this link **LINK** to see a short history of UK/NATO use.

Unfortunately the US MSDS to which 'Bill' refers is not to GHS but also does not provide the correct substance classification which must be used in the EU.

The European Chemicals Agency have published an assessment of ZTC which contains the following summary –

Substance Name: Pentazinc chromate octahydroxide

EC Number(s): 256-418-0

CAS Number(s): 49663-84-5

· The substance is identified as a substance meeting the criteria of Article 57 (a) of Regulation

(EC) 1907/2006 (REACH) owing to its classification as carcinogen 1A2 which corresponds to

classification as carcinogen category 13.

You can search for the article its in the public domain..

In Google search – Pentazinc chromate octahydroxide EC number – ECHA.

Jerry

[Ian S CParticipant @iansc]

When I rebuilt a Stuart Turner S9, I stripped the original chipped paint, and primed it with some Zinc Chromate based green coloured primer that I found buried under the *** (stores dept) in the workshop, don't know where it came from, but that with enamel paint on top, all brushed, and rubbed down between coats looks good, and doesn't fall off. This is on cast iron, not aluminium, but it does work well on aluminium.

Ian S C

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