Painting an Aluminium Chassis

[RoadrunnerOZ]

Does anyone happen to know if there are DIN numbers for the finishes on Neumann equipment? Specifically on Neumann disc cutting equipment.

I’ve never liked painting. I avoid house painting like the plague. So why am I into painting these boxes?

I have a Neumann lathe that needs a paint job. I am loath to disassemble it and send it off to be done commercially. I am doubtful it will go back together as well. This has been the main sticking point preventing further work. It occurred to me last night that this might be the first step in figuring out how to paint it myself without total disassembly.

The best way to get a match is to go to an auto-body shop that has a spectrum analyser for paint colour matching or a paint supplier with the same. When working in the Luxury Supercar body shop we used one to match paint blow-ins to the surrounding paintwork on cars like Ferraris and Lamborghinis etc. as with time the paint ages and shifts away from original code spec. If you can get an area of paintwork that has not colour faded and get that analysed their computer will come up with the mix formula. You can then get that mixed in lacquer in a spray can you can then do yourself. The trick is masking with paper, sanding, cleaning then remasking using plastic - double layered to ensure absolutely NO overspray on any non paintable areas.
Suggestion from one of the lathe forums is this crowd but it depends on the original colour - cream or grey?:
https://www.ralcolorchart.com/ral-classic/grey-hueshttps://www.ralcolorchart.com/ral-classic/white-and-black-hues

 

[RoadrunnerOZ]

Maybe some pics of the lathe??

 

[Gold]

Maybe some pics of the lathe??

Yes, RAL, not DIN. The lighter color is the classic Neumann hammertone finish. I think it’s hammertone because it is not textured and seems to have a clear coat. The darker color I think is crinkle coat because it is textured.

 

[Gold]

Got my mask today. Ready for battle.

 

[RoadrunnerOZ]

Yes, RAL, not DIN. The lighter color is the classic Neumann hammertone finish. I think it’s hammertone because it is not textured and seems to have a clear coat. The darker color I think is crinkle coat because it is textured.

I think they’re both hammertone - the darker looks like a finer one - perhaps a photo with the light shining across the paint? Does it reflect light the same as the lighter colour? The trick will be finding these colours in a hammertone finish but they are classic colours and should be available in a close finish - you may have trouble getting them matched and made unless you can find a paint supplier who will mix and match hammertone for you.
Edit: if you can feel a roughish texture then the darker one may be wrinkle finish - bit hard to tell from the photos, VHT may have that colour in wrinkle.

 

[Gold]

I think they’re both hammertone - the darker looks like a finer one - perhaps a photo with the light shining across the paint?

I think you are right. The darker one looks like a finer hammertone. The texture is just where it is peeling. It’s smooth on the dark parts that aren’t peeling.

Does it reflect light the same as the lighter colour? The trick will be finding these colours in a hammertone finish but they are classic colours and should be available in a close finish - you may have trouble getting them matched and made unless you can find a paint supplier who will mix and match hammertone for you.

 

[RoadrunnerOZ]

I think you are right. The darker one looks like a finer hammertone. The texture is just where it is peeling. It’s smooth on the dark parts that aren’t peeling.

Hammertone silver or champagne maybe on the lighter colour (unless the slight yellow cast is lighting or ageing) and medium dark grey

 

[Gold]

Hammertone silver or champagne maybe on the lighter colour (unless the slight yellow cast is lighting or ageing) and medium dark grey

The yellowing is what I'm guessing is a clear coat. Can a glossy paint yellow as well if the gloss is part of the paint formulation?

 

[RoadrunnerOZ]

The yellowing is what I'm guessing is a clear coat. Can a glossy paint yellow as well if the gloss is part of the paint formulation?

Yes - for acrylic or lacquer paints the clear is part of the paint and yellows with age - it can migrate to the surface depending on the paint makeup (like hammertone gloss seems to do) when curing to form the gloss topcoat for single pack paint, but it (clear resins and nitrocellulose) usually is about 60%+ of the gloss paint anyway. Some finishes use a clear coat after painting even for single pack to give extra depth of shine and to smooth surface imperfections by sanding prior to final coat or going wet on wet. In clear coats there are no pigment solids like in coloured paints but they all contain polymer binders or some sort of binder.

 

[scott2000]

You need outdoor marine grade suitable paint though due to the salt air - you can always look at marine supply stores for advice on a source of paints and primers.

...going to be tackling those aluminum inserts 1st of the year.....Can't really find any white zinc primers.. I see greens, red/browns and this yellow one...
https://www.westmarine.com/moeller-zinc-phosphate-primer-spray-yellow-17450446.html
obviously don't want primer to show through years down the road.. Should this be primed with some white primer after?


I want to stick with cans.. Looking at this stuff for top coat
https://www.westmarine.com/pettit-p...MI9auhtvHmggMVFp5aBR17XAbfEAQYAiABEgJtP_D_BwE
it comes in spray cans from other places apparently
https://defender.com/en_us/pettit-e...v9e5S590UQyOC6ZnwQYyTkM18SBp8s#76=14&493=2072

 

[RoadrunnerOZ]

Don’t worry about the primer colour - it’s best to have a different contrasting colour to the aluminium and topcoat so you can see the coverage of the first primer and first topcoat - if spraying the topcoat do a mist coat first to get a uniform light bonding coat. Also for painting bare aluminium you need to ensure total coverage of the primer - you’ll need several coats. The primer won’t show through the topcoat.
Both paints look technically good.
As long as your primer is light coloured and a different colour to your topcoat AND the metal to visibly get full coverage of each surface by the two paints, ie. primer over aluminium & topcoat over primer.
Pre made panel replacements for automotive come in the original primer colours used to build the car - mainly light green, grey or black depending upon the final topcoat colour. IIRC green primed panels were for silver topcoats in a lot of cases. A white primer is difficult to paint over with a white topcoat and ensure full top cover. White primer over aluminium is also difficult under bright light.

 

[RoadrunnerOZ]

I want to stick with cans.. Looking at this stuff for top coat

What colour are you thinking of for your topcoat? Are you planning on spraying?

 

[scott2000]

What colour are you thinking of for your topcoat? Are you planning on spraying?

Thanks for that info!
I'm doing white topcoat and would like to just rattlecan. I have an airless I'd be willing to bring to the beach but only run water based through it. So I figured spray cans would be best. Don't want to deal with cleaning with solvents there.....I'm planning on setting up a spray booth in their garage as I have done before when doing the inside doors... Now there are black racedeck tiles in there on the floor so it should be fun.

 

[RoadrunnerOZ]

White topcoat = use coloured primer. Whatever you do don’t go over the coloured primer with white primer - you’re asking for trouble when you get to the topcoat unless you are a gun spraypainter and know your coverage is perfect - you won’t be able to tell how good your topcoat cover is with white on white - white will make the white topcoat brighter but light grey is the safer option. Don’t use black or deep brown primer - they’re only good for the darker contrast colours like blue, black, green etc. Marine primers are designed for the traditional below the waterline colours so you are a bit limited in choice but you are in a super saline environment so you need to get the best start coat possible.

 

[scott2000]

you won’t be able to tell how good your topcoat cover is with white on white

That makes complete sense and it's the first time I've ever heard it put that way. It's always been light primer(usually white) for white or light colors and the opposite for darker colors. There's even a push to tint primers in the same color although the primer would obviously be a lighter version. Talking water base acrylics obviously.

I'm usually obsessed with the way a finish looks and usually catch poor coverage but with these irregular surfaces, I doubt I'd even be able to see misses without using different colors as you say...

Thanks. It's kinda a similar mindset to using a guide coat when sanding to really be able to see what's happening.. awesome advice..

 

[RoadrunnerOZ]

Tinting the primer towards the topcoat leads to a more uniform finish and less topcoat required - in commercial applications where your coats are based on cost the less paint you use the better - in automotive you use what the manufacturer used or the colours will be horribly different from where you paint to the rest of the car and for cheaper cars the total thickness of all coats can be even less than 100 microns, more expensive around 130 up varying depending on panel position/curvature - you don’t get much to play with. For factory finish on the likes of Ferraris we had to match everything - primer colour and total paint thickness included (we used paint thickness gauges to match up) - but for marine environment buildups you want heavy primer, heavy topcoat. When I worked building racing yachts in NZ the idea of different primer colours to topcoats was to achieve total coverage at each stage of the process keeping paint volume down as each yacht had to be as light as possible. I have used this method for DIY or in vintage synthesiser restorations ever since.
Many years ago I learned how transparent paint was when I set fire to some cooking oil on the stovetop (falafels!) and had to repaint the kitchen ceiling before a landlord’s inspection due in two days - it took ages and a lot of paint for the ceiling to go from swirly black on white (it would not clean off) to swirly grey to finally white - just in time so we didn’t get evicted.
Edit: the reason I mention this is your topcoat is white so a light coloured primer helps your topcoat look the best - coloured paint is a mix of tiny pigment particle solids and clear resin and binders - previous colours will show through faintly via the gaps between pigment particles. .

 

[KLDVOX]

sorry to say this, but to be honest as an engineer i cant really see the point in repaintng a machine tool unless you want it as an ornament or are planing too sell it. by the very nature of the materials you will be turning the paint will be scratched and chipped by the time you have done 4 or 5 jobs. my lathe has had a fair amount of use, it is scratched and chipped but will not rust or suffer from corrosion as it also has a uniform fine layer of oil on just about every last part.
thats just my penny worth, guess im the odd one out

 

[RoadrunnerOZ]

sorry to say this, but to be honest as an engineer i cant really see the point in repaintng a machine tool unless you want it as an ornament or are planing too sell it. by the very nature of the materials you will be turning the paint will be scratched and chipped by the time you have done 4 or 5 jobs. my lathe has had a fair amount of use, it is scratched and chipped but will not rust or suffer from corrosion as it also has a uniform fine layer of oil on just about every last part.
thats just my penny worth, guess im the odd one out

This is a record cutting lathe - a big difference to an engineering metalworking lathe. There are no flying bits of metal or cutting oil getting over everything. They are also collectors items.

 

[KLDVOX]

thank you for correctig my ignorance. i fully agree it should be revived and given anew lease of life. i stand corrected

 

[scott2000]

Started stripping those aluminum inserts. One more pass and some extra love and they'll be good . Haven't even pressure washed yet...May just try that first now that there's barely any paint left...

So, if guessing, the manufacturer buys or has pieces that are pre-primed with what looks like a 2k epoxy but idk. It's stuck for good.

Then they grind it back to be able to weld. But then don't go back and prime the weld areas or even the 2 larger end pieces of bare aluminum they most likely add for the top and bottom. That paint was coming off before stripping even started.

So the plan is to just shoot some self etch on the bare areas? I want to spray all of it with the self etch. Maybe if it is epoxy primer, the self etch will give the top coat an easier grab??
ugh...