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Painting Brass

Adhesion Promoter

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Stub Mandrel21/07/2012 21:39:48
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Carefully scanning the shelves in Halfords, IO could find no sign of etch primer, but I found a single can of 'adhesion promoter' suitable for "plastics and non-ferrous metals".

It is a clear, satin finish lacquer that goes on quite liquid - oddly it either sets or runs, and having put on too much it collected in a corner as a pool I was able to wipe off, without damaging the adjacent area - most odd. I applied two coats.

I note my acrylic primer suggests using this type of product on plastic, but doesn't mention non-ferrous metals. A single, light coat of primer has gone on top very nicely, but of course the acid test is how long it lasts.

Neil

Chris Trice22/07/2012 00:29:17
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1362 forum posts
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Halfords do do an etch primer but to be honest, not much really grabs brass. I've done a LOT of brass work and found the best is the ICI two pack etch primer, the yellow green type they use on aircraft and aluminium bodied cars. It has its own catalyst and thinner. You only need to spray on a very thin but wet coat. I know the other approach, which I haven't personally tried but I'm reliably informed works in critical situations, is to have the brass item nickel plated. Paint takes to Nickel far more readily.

Steambuff22/07/2012 01:05:46
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511 forum posts
7 photos

I have always used either - Teroson Etch Primer Aerosol for Metal & Plastics. (C+L Finescale supply it) or the Phoenix Paints etch primer.

I always use the latter if I am going to use a Phonix top coat.

Dave

Springbok22/07/2012 05:41:10
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879 forum posts
34 photos

On brass you need a good etch primer Phoenix is good but I think a bit pricy. So it really depends on the volume area you wish to prime. Though on saying that used some on a 7.25g loco I built and still have a little left.

Chris Vine's book is a treasure trove of info on this subject.

Bob

Stewart Hart22/07/2012 07:35:44
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654 forum posts
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I've always used Phoenix etch primer also but as said its a bit pricy, but the small pack is enough to paint 3 or 4 small engines, it does start to seperate out after about 18 months though.

Always on the look out for an alternative I found out that Hammerite does a spray can of etch primer for use with their paints so going to give that a try next. As any one got any reports on this product ?.

Stew

Stub Mandrel23/07/2012 20:45:43
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4311 forum posts
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First impressions of this stuff are good. I 'softened' all corners with abrasive covered foam blocks, and both primer and paint have gone on without thinning at these vulnerable points. The handling involved in spraying so far has not caused any chips - this is in contrast to the funnel for my boiler, which was primer straight on copper tube, which seems to lose paint simply by beinmg picked up.

Bob-

I was hoping no-one would mention Chris Vine, I got my wife to buy me the book for a birthday present and it gives me nightmares. I grew up with weathered and battle-damaged airfix kits (even the airliners)!

Neil

the artfull-codger09/10/2012 19:53:41
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255 forum posts

As Chris Trice says ici etch primer, I use it for alloy,brass,steel & everything else, I painted some alloy castings I made with cellulose primer & the stuff just chipped off with my fingernail,I blasted it all off & brushed on [no need to spray as it's self levelling] ici 2pack etch, I could not scrape it off at all & I've sprayed enamels,cellulose & 2k on top of it & no bother,as with any paint job you need a good primer, I accidently spilled some on my tea mug [glazed surface]in the workshop & it went through the dishwasher for over a year & didn't wash off & dishwashers take the logo's of most mugs!!eventually, I've not used it but 2pack epoxy primer is even better as it's water resistant so you can prime frames etc & leave it for yrs.

Stub Mandrel09/10/2012 21:40:04
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4311 forum posts
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Thanks,

I'm not 100% convinced by the adhesion promoter. next time I will go for proper acid etch primer, but I hate painting so I won't be stripping it all down and starting again.

Neil

Rustkolector26/10/2012 05:02:40
6 forum posts

I like building with brass and have had little previous success with any normal paint types on brass. In my experience, paints and primers have little adhesion to brass. They especially chip around nuts and bolt heads, and sharp edges. I recently tried a heat curing finish that requires #120 Alum oxide grit blasting which I normally do anyway to erase filing and machining marks. These finishes, I believe, were developed for military firearms. For the last two years, the finish has proven impervious to any solvent I have used and absolutely does not chip around fasterners. I usually paint all my parts individually prior to final assembly. The drawbacks I see are that it is only removable by grit blasting, colors are limited, and it is only available in satin or matte finishes.

Jeff

Versaboss26/10/2012 11:15:32
458 forum posts
51 photos
Posted by Rustkolector on 26/10/2012 05:02:40:

..... I recently tried a heat curing finish that requires #120 Alum oxide grit blasting which I normally do anyway to erase filing and machining marks. .....

Jeff

Wow, wow, Jeff, and if now you would give us also the brand name of that paint and where you got it and in which country then your posting #1 would be perfect!!!

Greetings, Hansrudolf

Terryd26/10/2012 12:13:16
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1935 forum posts
179 photos
Posted by MICHAEL WILLIAMS on 09/10/2012 20:59:43:

Hi Neil ,

A long forgotten method of getting paint to stick to brass was to acid etch the surface , wash , dry , warm slightly and then paint - with the whole sequence being done as fast as possible to prevent re degredation of brass surface .

Don't know what chemical was actually used but probably something like a PCB etchant but in very dilute form .

Regards ,

Michael Williams .


Hi Neil,

This process is used by some scratchbuilders in the model railway world. The chemical used is ferric chloride which as you say is used in pcb etching. The etching ruins the brass colour (!) but apparently the acrylic auto paints used afterwards adheres quite well. I've not tried it myself though, but I have a couple of scratch built 0 gauge locos that I need to paint soon so I may give it a try. Probably test various etches though first - I have been working with copper chloride etch for pcbs recently and it works well, how well it will work with brass I know not as I haven't tested it but will report when I do.

Regards

Terry

tractionengine4226/10/2012 13:55:11
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377 forum posts
110 photos

Rather than using an etch primer you could try Polyester Spray Filler as a base which I think sticks to almost anything (after the part has had a good degraese and clean), it's like a body filler that you spray on. Some can be thinned depending on the brand. Like body filler it has a resin and hardener.

After it has dried rub it down and apply a primer (but not etch primer) ready for painting.

It's used on machine castings, car restoration and the like.

Normally it has a limited shelf life and not cheap. May not be good on fine detailed models unless you can thin it right down, other wise it will fill in the detail.

 

Nigel

Edited By tractionengine42 on 26/10/2012 13:58:19

David Littlewood26/10/2012 15:34:43
533 forum posts

Just a thought, if someone wants to try some experimentation: try electroless tin plating the brass. I have done this a few times, it almost instantly gives a coat of tin several microns thick which seems to adhere well. I have not tried painting it, so you can do your own testing! Available here: **LINK**

...but you can make up the solutions yourself at considerably lower cost.

David

Rustkolector26/10/2012 17:51:40
6 forum posts

Hansrudolf,

Sorry for the product omission. The product is called Gun Kote 2400 **LINK**. I suggest you browse their website for more detailed information. For some reason, paint adherance and chip resistance on brass is considered by most paint manufacturers to be quite difficult. KG Coatings was the only manufacturer I found that would guarantee their finish for adherance and chip resistance,.....and I called a lot of paint companies. I had trouble with a head gasket on one engine. The gasket was replaced three times before the right material was found. The paint under the head hold down nuts was just beginning to show some scuffing but no chipping. One model engine I have cleaned a few times with aerosol automotive brake cleaner solvent. This is a very aggressive solvent and it does not affect the Gun Kote finish or sheen. It isn't inexpensive, but you will only have to paint your model once. I am just a satisfied KG Coatings customer, nothing more!

It is distributed in Italy and the UK, as well as Australia, New Zealand, and Japan.

Jeff

Michael Gilligan26/10/2012 18:30:52
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16638 forum posts
725 photos
Posted by Rustkolector on 26/10/2012 17:51:40:

It isn't inexpensive, but you will only have to paint your model once. I am just a satisfied KG Coatings customer, nothing more!

It is distributed in Italy and the UK, as well as Australia, New Zealand, and Japan.

Jeff

 

Jeff,

If it's as good as you say; and available in the UK at anythinhg like the listed US price ... it looks a bargain!

Many thanks for the info.

MichaelG.

.

P.S. I just discovered Open Season named as the U.K. distributor.

 

Edited By Michael Gilligan on 26/10/2012 19:10:31

Versaboss26/10/2012 19:05:41
458 forum posts
51 photos

Many thanks Jeff, yes it seems to be very good stuff they offer. Just hope I remember this when the need arises... wink

Greetings, Hansrudolf

Stub Mandrel26/10/2012 19:17:55
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4311 forum posts
291 photos
1 articles

Ferric chloride etches brass as well as it does copper PCBs. I did these using PCB making UV resist spray and ferric:

I hadn't realised at teh time, but yes thathumbrol black enamel adhered really well to the etched surface!

Neil

Makers PlateHudswell Clarke Locomotive Plate

KWIL26/10/2012 19:23:21
3322 forum posts
63 photos

Open Season Limited T= 01865 891773 E= rupert@openseasonltd.com

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