Author Topic: Etch Primer  (Read 6972 times)

Offline vcutajar

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Etch Primer
« on: November 15, 2014, 09:33:05 AM »
Hi guys

I would like to tap the collective knowledge of the group.

After a break from the Corliss I am back at it again.  Next in line for finishing is the flywheel.  I would like to add some bits to it and was thinking of using aluminium because I have the right size.

I have read that one needs to use etch primer before painting but I can't get hold of small quantities for what I need.  Is there an alternative to this etch primer?  Does the paint really peel off if it is not used?  Can I use zinc chromate paint (if it is still available)?

My other option is to be done with it and use mild steel instead.

Thank you in anticipation.

Vince

Offline Jo

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Re: Etch Primer
« Reply #1 on: November 15, 2014, 11:39:04 AM »
Hi Vince,

You should find that Etch primer is available in car spray (rattle) cans these days ;)

Jo
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Arbalest

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Re: Etch Primer
« Reply #2 on: November 15, 2014, 11:52:27 AM »
Yes, Halfords normally have it. If possible sand blasting also helps the paint stick.

Offline Stuart

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Re: Etch Primer
« Reply #3 on: November 15, 2014, 11:53:54 AM »
yes it will peel off very easily

Do they have Halfords in Malta ?

Stuart
My aim is for a accurate part with a good finish

Offline vcutajar

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Re: Etch Primer
« Reply #4 on: November 15, 2014, 12:04:35 PM »
Thanks guys for the replies.

Unfortunately we don't have Halfords here and all the primer spray cans I have seen here do not specify that they are etch primers or maybe suitable for aluminum.

Looks like the parts are going to be made with BMS after all.

Vince

Offline Stuart

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Re: Etch Primer
« Reply #5 on: November 15, 2014, 12:19:44 PM »
Vince

Didn't think you did but here is a description of the rattle can stuff

The U-POL Acid #8 Etch Primer promotes paint adhesion to difficult substrates such as galvanised steel and aluminium. It is ideal for rub throughs in primer prior to application of colour and it features a fast drying formula

Maybe a search in your neck of the woods
I do know that Amazon do a something similar

Stuart
My aim is for a accurate part with a good finish

Offline Ian S C

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Re: Etch Primer
« Reply #6 on: November 15, 2014, 01:15:03 PM »
Vince, I'd go Zinc Chromate For Aluminium.  Humbrol produce little tins of it.  Cessna 185B rebuild, zinc chromate primer,  about 80% new skins etc.
Ian S C
« Last Edit: November 15, 2014, 01:21:18 PM by Ian S C »

Offline tangler

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Re: Etch Primer
« Reply #7 on: November 15, 2014, 01:27:01 PM »
Vince,

I defer to the expertise above but I sprayed the ally castings for my Wyvern with ordinary automobile grey primer followed by a filler primer and then a top coat.  The paint has also adhered to the couple of bronze bits and the copper fuel tank.   Admittedly that was only 6 months ago but it's OK so far.  When I had to scrape off the over spray it seemed pretty adherent, much the same as on the cast iron bits.  Preparation was just a wipe over with acetone followed by a scrub with detergent and water.

Just my tuppenceworth,

Rod

Offline Don1966

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Re: Etch Primer
« Reply #8 on: November 15, 2014, 02:49:41 PM »
Vince I with Ian on this the zinc chromate should work real good. Just make sure you clean the surface properly. If you have a way to bead blast it that's even better.

Don

Offline Ramon

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Re: Etch Primer
« Reply #9 on: November 15, 2014, 03:50:27 PM »
Hi Vince I concur with the Zinc Chromate and Grey primer can adhere quite well until perhaps it gets a chip - it's then that it begins to delaminate. A long way back I made an 'all singing etc' control line handle and carved the handle part from ali. Primed with grey primer and sprayed a deep yellow it was gifted as an award at the annual champs. Though I say it myself, with all the steel parts blackadised it did look the business. Imagine my disappointment sometime later then, when the recipient told me he had dropped it on the tarmac and the paint literally fell off the handle like a broken eggshell ::)

If it's possible - given the part - a light coating of JB Weld will really bond well (Yes, I know, I have shares in the company, ;D) - lightly rubbed down that will take any primer/top coat.

Something to be aware of too with some self etch primers is that after application the time before coating over should, up to a point, be as long as possible as apparently, application of the next coat arrests the etching capabilities - ie the longer the time the better the etching process.

Hope that's of use - Ramon

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Offline the artfull-codger

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Re: Etch Primer
« Reply #10 on: November 15, 2014, 08:51:55 PM »
Hi,
   My 2 penneth worth,I've done quite a lot of castings in alloy & painted them with various paints but the best primer I've used is ici two part etch primer,then enamel afterwards,the etch primer[the most important bit] has never chipped or flaked off on alloy brass or steel, I'm led to believe that epoxy primer is even better but I've not used it, I painted some alloy plaques I cast with ''hammerite'' smooth & no primer & you could scrape it off with your fingernail but I use hammerite[smooth] after self etch priming o-k.

Offline vcutajar

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Re: Etch Primer
« Reply #11 on: December 24, 2014, 11:04:05 AM »
In my quest to find a primer for aluminium I found this spray can.  It does not say it is an etch primer but it says it is for aluminium.  I guess time will tell.

Vince

Offline Allen Smithee

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Re: Etch Primer
« Reply #12 on: December 24, 2014, 02:34:15 PM »
Vince, I'd go Zinc Chromate For Aluminium.  Humbrol produce little tins of it.  Cessna 185B rebuild, zinc chromate primer,  about 80% new skins etc.
Ian S C

I may be wrong, but it's my understanding that the small tins produced by Humbrol contain enamel paint that is the colour of zinc chromate primer, for use on plastic model kits. I don't believe it's actually zinc chromate primer.

AS
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Offline Steam Haulage

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Re: Etch Primer
« Reply #13 on: December 24, 2014, 03:43:30 PM »
Am I allowed to interfere in this thread?

After more years in the UK paint industry than I care to think about I have accumulated a lot of knowledge, some of it questionable, about paint formulation, manufacture and usage.

If I am permitted I might be able to give some background and illumination about etch primers, especially on reactive metals like aluminium.

Jerry :old:
Dogs look up to you, cats look down on you, pigs treat you as equal.

Offline Stuart

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Re: Etch Primer
« Reply #14 on: December 24, 2014, 05:03:45 PM »
All I will say Jerry is get on with the enlightenment I for one hate painting with a passion any information that will ease my hate and loathing for that unforgiving coloured liquid will be greatly received 😳

Stuart
My aim is for a accurate part with a good finish