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Suitable primer for painting aluminium?

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Nick T01/11/2014 16:38:59
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53 forum posts
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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

donkey01/11/2014 17:02:45
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70 forum posts
5 photos

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

brian

Bob Brown 101/11/2014 17:14:18
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982 forum posts
125 photos

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 T01/11/2014 17:22:23
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53 forum posts
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Thanks for the advice Bob & Brian - much appreciated.

Nick

"Bill Hancox"02/11/2014 00:03:13
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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

Scott02/11/2014 08:54:10
52 forum posts
10 photos

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

HomeUse02/11/2014 09:35:13
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168 forum posts
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Zink Chromate primer is available on EBay and in many D I Y shops - would recommend for use on alloyyes

ronan walsh02/11/2014 09:46:52
539 forum posts
32 photos

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 W02/11/2014 10:03:57
2011 forum posts

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.

Hopper02/11/2014 11:06:22
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3699 forum posts
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Rub the job down with vinegar before applying regular primer. The vinegar etches into the ally so the primer can stick to it.

frank brown02/11/2014 12:32:30
436 forum posts
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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 C03/11/2014 09:45:06
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7447 forum posts
230 photos

We used Zinc Chromate primer on all aircraft painting, and most of our aircraft were painted with two part epoxy paint. Ian S CCessna 185 B ZK-CFI

NJH03/11/2014 09:53:14
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2314 forum posts
139 photos

I agree with Ian

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

Norman

Oompa Lumpa03/11/2014 12:13:28
888 forum posts
271 photos

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 Gilligan03/11/2014 13:38:11
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13983 forum posts
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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 Gilligan03/11/2014 14:37:34
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13983 forum posts
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Here is the MSDS for Jenolite.

Nick Hughes03/11/2014 15:46:35
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200 forum posts
129 photos

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

Neil Wyatt03/11/2014 18:10:36
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Moderator
16562 forum posts
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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 103/11/2014 18:42:54
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982 forum posts
125 photos

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

Bob

mike T03/11/2014 20:54:27
167 forum posts
1 photos

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

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