Etching Brass for Painting

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one_inch_railroad
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Etching Brass for Painting

Post by one_inch_railroad »

A friend of mine has a brass caboose he wants me to paint. I am going to use self-etching primer but I find that alone isn't always enough to get the paint to adhere well to the brass. He suggested we should etch the brass prior to applying the self-etch primer.

What works best for etching brass, how long should it be left on for and should the solution be washed off with water to stop the etching process prior to applying the primer.
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Re: Etching Brass for Painting

Post by Mike Walsh »

Calling Jack Bodenmann….
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Harold_V
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Re: Etching Brass for Painting

Post by Harold_V »

One thing you can consider is the use of sulfuric acid. It readily dissolves zinc and copper oxide, but does not dissolve elemental copper unless the sulfuric is heated and concentrated. By leaching out the surface zinc, you'll honeycomb the surface, providing tooth for the paint to grip.

Sulfuric acid is readily available from most parts stores as battery electrolyte. It's already diluted. It can also be removed from old lead/sulfuric car batteries.

Should you elect to go that route, please remember that pouring water in to sulfuric acid is an accident waiting to happen. There's so much heat evolved that you can experience a steam/acid explosion. If you must add water, be certain to add the acid to the water, all the while stirring constantly. Use a glass rod for stirring. Avoid using any metallic vessels, as most of them will be readily dissolved by sulfuric acid. Wear protective gloves and face gear.

H
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Re: Etching Brass for Painting

Post by rkcarguy »

Anytime I have used a chemical etching solution on anything with holes/rivets/screws, a little of it always seems to remain and then the paint peels around those features. It's ever so slightly, even if you do a really good job cleaning up after it's been etched. The only success I've had is doing the chemical etching on the raw sheet material BEFORE you start a project. When it's something that is already built, I use only sandpaper, scotch-brite, and/or stainless wire brushes to profile the material for paint adhesion.
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Bill Shields
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Re: Etching Brass for Painting

Post by Bill Shields »

my favorite is self-etching primer from Precision Paints in the UK.

two components you mix, then spray it on with an air brush...it is dead clear..

Then you put paint on top of it.

never seen anything like it from anywhere else...and the paint is still on my copper / brass Hudson & tender 40 years later...
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Re: Etching Brass for Painting

Post by Glenn Brooks »

Pettit Paint makes a marine grade etching primer that they advertise makes an excellent bond with yellow metals, such as brass and bronze, also stainless, and mild steel. Might be worth exploring.

https://www.pettitpaint.com/media/3372/ ... imer-1.pdf

Also, maybe follow that up with a coat of marine epoxy primer, then your preferred top coat. I’ve found marine single part epoxy or urethane topside coatings, particular undercoat, to be the longest lasting, most durable paint I’ve ever used. Usually I use interlux, but apparently now Petit has this metal primer formulation specifically for speciality jobs like brass and stainless.

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Re: Etching Brass for Painting

Post by ccvstmr »

One Inch...from your description, get the feeling you're NOT talking about a 1" or 1.5" scale caboose. Don't think anybody in these scale sizes would fabricate a caboose in brass. Therefore, suspect you're talking (maybe) an HO or O gauge caboose.

Don't know how practical this might be, but I sand blast as much of my metal work as possible before painting. Usually apply paints over the roughened bare metal surfaces. Not only does this clean the metal surface, but gives the paint (and/or primer) something to get a bite on the metal surface. Have used this method for a number of different metal surfaces...brass included.

If yours is a table top model, might consider a glass bead blast...this is not as aggressive on the metal surface. Good luck. Carl B.
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Bill Shields
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Re: Etching Brass for Painting

Post by Bill Shields »

blasting does clean the surface off...but i have often found that blasted brass sheet is no longer FLAT BRASS sheet.

something do to with stress relieving one side....like CRS.

I am getting ready to do a 1" scale tender that is all brass....and it's a LOT of cleaning...so I am all ears...
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JBodenmann
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Re: Etching Brass for Painting

Post by JBodenmann »

Hello My Friends
When painting brass I will first de grease with something like Purple Power de greaser. This is only if your parts are greasy or oily. Then use Ospho or similar product to clean the brass. Use a red scotch bite pad to scrub flat areas and a tooth brush for around rivets and details. Sometimes I will use a stainless or brass platers scratch brush. This is basically a tooth brush with metal bristles. This will de-oxidize the metal and get it nice and bright. Then give everything a thorough rinse with clean water. Dry everything with clean towels and compressed air. Use a tack rag to remove any lint or dust and paint immediately. Use self etching primer, there are many good brands, Rustoleum, NAPA sells very good etching primer, also Ace Hardware. Then your favorite top coat. Preparation is the important part. I do the same for steel and aluminum. The Ospho is the important part, getting all the oxides off and brightening the metal is the ticket. Works for me :D
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Bill Shields
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Re: Etching Brass for Painting

Post by Bill Shields »

Jack:

Blasted brass with glass beads (have a booth with clean beads in it)-> washed with acetone -> allow dry -> dunked in ospho (small part)-> allowed to dry (turned grey-ish) -> kept greasy hands off of it -> air brushed SEM self etching primer on -> stuff looks like black water ..is very thin comes in quart cans at reasonable $$ -> stuck like glue..can hardly scratch it off...really like that ospho stuff...

thanks for advice! think have a 'process' to apply to the entire tender
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Harold_V
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Re: Etching Brass for Painting

Post by Harold_V »

Hmmmm. I dunno, Bill. Sharp abrasive would be a better choice than beads, as it cuts the surface and creates better tooth than beads, which peen instead.

Just sayin'

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Bill Shields
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Re: Etching Brass for Painting

Post by Bill Shields »

I agree but beads is what I have
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