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Painting Brass Chassis


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#1 Ember

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Posted 10 February 2015 - 09:26 AM

I wasn't originally planning on painting the brass I'm currently working on, but the mounting screws I'm using are black and spoil the 'jewelry' finish a little. So, black it will be.

should I use an etch primer on it? And will an automotive paint be more resilient on the brass than a model paint?
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#2 kalbfellp

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Posted 10 February 2015 - 10:20 AM

I sandblast any brass chassis that I intend to paint,then use Auto paint. it is much harder than model paint and drying time is much better.
I usually paint the suspension chrome or silver.
Etch primer would certainly help.

#3 Ember

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Posted 10 February 2015 - 10:42 AM

No suspension on this one Phil. It's for my IPS Porsche.
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#4 Ontheflipside

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Posted 10 February 2015 - 11:56 AM

Check your local hardware store. Someone used to make a spray lacquer for copper and brass. Use that as primer 1st.
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#5 kash15394

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Posted 10 February 2015 - 12:03 PM

Etch Primer....Yes
Auto paint....Yes

#6 Old johnny

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Posted 10 February 2015 - 02:15 PM

Etch or you could try a really good working over with steel wool...anything to get through the oxides, and remove any traces of flux..keep the coats really thin.

#7 slotbaker

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Posted 10 February 2015 - 02:24 PM

View PostOntheflipside, on 10 February 2015 - 11:56 AM, said:

Someone used to make a spray lacquer for copper and brass. Use that as primer 1st.
Wattyl Incralac?
:huh:
Steve K.

#8 rosco01

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Posted 10 February 2015 - 05:13 PM

Hi Ember - we've discussed the use of SEM black etch before - and as Phil states, if you key up the target - most primers will bond quite well.. more particularly those designed for purpose - etch primers.

I found another product when spraying 1:1 vehicles which works extremely well on most substrates.
It looks like translucent yellow.....ummmmm trying to keep it nice - think you know what I mean - and really bonds to just about anything.
It's a 1k etch primer and I believe it would lend itself well to our purposes...
Sadly, you have to purchase a litre of the stuff.

A little bit of info might go a long way to explain why I like the stuff.

The product is called "Protec 421-2208".
It touch dries in 5 - 10 minutes (quicker if more thinners are added) and can be either re-coated or over-sprayed in 30 minutes.

It is recommended to thin with automotive lacquer thinners (not modeling lacquer) by 20 - 30%...but for our application through an airbrush - I intend to thin mine at around the 1:1 mark (50%) and build up two very fine coats until it has a sound base - not thick, but certainly no bare patches.

Unlike many other etches or primers, this one is intended for bare steel - which will cause major issues if ordinary primers are used and moisture is trapped between it and the metal. You see this nearly every day when back-yarders spray cars... the primer is left for yonks to "pull down" before blocking back - and if a proper etch has not been used - rust stains in the paint begin to show through.
Even if over-coated in a short time-frame, the damage progresses underneath (automotive acrylic paints actually "breath")... and poorly prepared bare steel doesn't take too long to show up through the top coats... enough, you don't need all this... I'll just explain a little bit on why this stuff should be used in lieu of an ordinary primer... basically, it's the added components which both etch the metal and coat it..

To do this, it has a couple of "nastys"... 6.4% chromium and 2.5% lead (both in the dried film state) - so, spraying in a room is out of the question and I would thoroughly recommend use of at least a paint grade face mask.... as you would use for all automotive paints - even when using an airbrush.

The data sheet shows it to be satisfactory on non ferrous metals and other substrates - so, I'm hopeful that when I come to etching my brass and piano wire - it will both bond well and also provide some down the track protection against rust.

Phil recommends "tinning" piano wire when making chassis - and I believe this to also be important in protecting them once they are covered in paint.
The lead content of this product suggests to me that it will bond nicely with any tinned piano wire. I do know it bonds well with brass.... and all other alloys.... I have used it when etch coating the white metal of an automotive horn plus some alloy parts (windscreen wiper motor base etc., etc.,).

I will be experimenting with this when I finally get my little Cooper chassis finished (WIP) and will use the Badger to feint a fine mist coat of this over it prior to a primer and perhaps to mist top-coats and a sealer.

The SEM has been good for brass and white metal locomotive etching... I am firmly of the opinion that it is a ground down version of an automotive product.. but not the one which I'm recommending above. This stuff it will peel/flake/rub off anything which is not keyed... and I don't for one moment suggest raking great furrows in anything to key it..... 800 wet and dry is sufficient... cross-hatched on rod work like piano wire, and for styrene card - simply rubbing off the sheen is sufficient.

It certainly bonds well with styrene card and locomotive "plastic"... but I have suffered failure using it over existing paintwork... it simply peels off - there must be some incompatibility with something in cured enamels and automotive acrylic top coats...like those offered by SEM for color coating models....... all this chemistry compatibility stuff is well beyond my knowledge.

The automotive 1K etch (Protec 421) will actually "bite" into the surface of metals (not that you would know - when blocked back to bare - it simply has "dulled" the surface.. but, for all intents and purposes - it "etches").

I'm far from painting anything metal yet... but will make comment and post pix as I reach that stage.

I fully anticipate that this Protec will be my first line of attack.. if it shows any sign of lifting or resisting the following Tamiya primer - I'll revert back to SEM etch black.

frats,
Rosco

Edited by rosco01, 10 February 2015 - 05:25 PM.


#9 Ontheflipside

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Posted 10 February 2015 - 05:32 PM

View Postslotbaker, on 10 February 2015 - 02:24 PM, said:

View PostOntheflipside, on 10 February 2015 - 11:56 AM, said:

Someone used to make a spray lacquer for copper and brass. Use that as primer 1st.
Wattyl Incralac?
:huh:

I can't believe that I wanted to grow up

Mount Salt Panorama Track Combined Road and Rally Track built near Salt Pan Creek Padstow - Sydney

A quick build rally track

2017 WRP Round 11 at Mt Salt Panorama

https://i128.photobu...zpss7sqiwfj.jpg

#10 Ontheflipside

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Posted 10 February 2015 - 05:33 PM

View PostOntheflipside, on 10 February 2015 - 05:32 PM, said:

View Postslotbaker, on 10 February 2015 - 02:24 PM, said:

View PostOntheflipside, on 10 February 2015 - 11:56 AM, said:

Someone used to make a spray lacquer for copper and brass. Use that as primer 1st.
Wattyl Incralac?
:huh:
yep
I can't believe that I wanted to grow up

Mount Salt Panorama Track Combined Road and Rally Track built near Salt Pan Creek Padstow - Sydney

A quick build rally track

2017 WRP Round 11 at Mt Salt Panorama

https://i128.photobu...zpss7sqiwfj.jpg

#11 kalbfellp

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Posted 10 February 2015 - 05:36 PM

Lynne if you grovel to the local bodyworks they may just decant off a small amount of etch primer for you.
We used a Dulux product to etch aluminium sheets that we used for sign making.
These signs were then sprayed with Auto acrylic and baked, I still have several that are over 20 years old and still in great condition.
Just too labour intensive for today's market,could not compete with Vinyl die cut on price.

#12 Ember

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Posted 10 February 2015 - 06:42 PM

Not a problem. I actually have a can of etch primer from a few other repair jobs. Sprayed it with etch this afternoon.

I have some of the model etch we were talking about Ross. They no longer make it in black, but the dark grey is lined up ready to be used on the next fine job. I was just in a hurry to get the brass chassis hit with something so I can tick this proxy car off the to do list. The Lotus is almost back on track again after its little disaster.

Thanks for the details on the Wattyl stuff. I'll investigate it. Might be useful on the bathroom taps, the worst job of cleaning an antiquated bathroom.

Phil, no amount of sweet talking local spray painters will get them to give anything away. I tried it just to get some mixing pots.
Computers. They'll never catch on.

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#13 rosco01

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Posted 10 February 2015 - 07:39 PM

Glad you have the SEM etch, Lynne - be interested to learn what you think of it..... just remember - keep it "wet" or it will spread gossamer everywhere.
You can really thin the stuff down with meths... and then drop your pressure.
You might also like to try straining it prior to filling you paint cup.... the stuff is strange, rest assured - but it does perform when you get used to it.
The grey is a funny little product - when it dries, you'll see strange yellow bands and shapes in it...
You can sand (almost polish) it once cured right out and it becomes a great base from which to build on - finely applied as you should try to use it.

As for auto spray painters, detailers, paint suppliers... there's a "guild" here.... if you are an "outsider" - you stay there. It's almost like they have taken an oath in trade secrecy...

My education has assembled from self-taught experience - and dropping the right terminology on unsuspecting ears over counters.... you have to put the missing blanks together, but you can work through their shield of silence until you are unmasked (excuse pun).

Glad you have braved the etch, Lynne - and I do hope you have found success with the new gun.... I have yet to go for a double action.. just not that confident to bite the bullet and purchase one.
Having said that - in full scale spray painting, I suppose I have them already.. but not for airbrushing...

Ok - the Lotus...?.... I expect work on the body continues...?

I'm just about set to start work on my suspension detail... not looking forward to it.. I know what I want to achieve - and I believe I'm aiming far too high for a first model.... we'll see...

Let me know if I can send you some of this Protec... let me shoot some on a chassis first, if it works - I'm up for sending a small jar full over the land to you.....

Oh, and before I forget - the "light putty" - I have procured some from Honkers... might be three weeks until it gets here.. but $16.02 shipped was a great price.... I'd have it now if the local hobby shops stocked it.... Hobbies 4U here in Boronia no longer carry it.... and my LHS is in the throes of ditching all of one popular brand and stocking up in another which I do not use.....

frats,
Rosco

Edited by rosco01, 10 February 2015 - 07:41 PM.






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