v8kid
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| posted on 1/12/15 at 06:47 PM |
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Stripping paint from aluminium castings
I'm renovating a 1950 Colchester Triumph lathe and all the cover panels are cast aluminium - whats the best way to strip them and then clear
lacquer them?
I know aluminium does not like alkali (ie nitromors and the like) but would it be OK if it was neutralized afterwards with a weak acid i.e.
vinegar?
I have a bead blasting cabinet at work and although its not man enough to strip 65 years of hamfisted paint jobs it would clean up the black oxide
surface that alkalies leave and I'm OK with the slightly sanded finish not requiring a high polish.
What about the lacquer is there an issue with adhesion? What do the alloy refinishing boys use?
Cheers!
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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mark chandler
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| posted on 1/12/15 at 07:35 PM |
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If you were stripping paint off an aluminium bodied car chemicals would be the weapon of choice, on an old lathe its a no brainier.
I would finish off with a brass brush in a drill.
For painting forget laquer, upol acid etch and silver paint.
[Edited on 1/12/15 by mark chandler]
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v8kid
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| posted on 1/12/15 at 09:38 PM |
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quote:
Originally posted by mark chandler
For painting forget laquer, upol acid etch and silver paint.
[Edited on 1/12/15 by mark chandler]
Why?- what am I missing, whats wrong with lacquer indoors?
I would like to keep the aluminium look and as its generally dry and warmish it will have an easier life than alloy wheels. Silver looks - well silver
and sparkly.
Although not entirely appropriate to 65 years old as opposed to aluminium - I can see your point its just that's not where I want to go 
I had thought of waxing but splashes from soluble coolant would probably mark it - could I just leave it as bare ally?
Cheers!
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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mark chandler
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| posted on 1/12/15 at 10:00 PM |
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I just think as curls of of hot swarf come off the lacquer will quickly scratch up, my old Harrison is painted grey and gets washed down with whites
spirits after use. I do not believe leaving bare will work as you need a coating to smooth the surface.
If you refaced a brake disc for example the cast creates handfuls of black dust that makes a complete mess of everything.
A plain paint finish is easier to maintain in my experience, horses for courses.
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Phil.J
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| posted on 2/12/15 at 08:03 AM |
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Old machine tools like lathes were coated in a sort of thick filler ti hide all the casting imperfections and sand grain. If you strip this off you
may end up with a fairly rough looking finish.
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MikeRJ
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| posted on 2/12/15 at 09:02 AM |
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quote:
Originally posted by Phil.J
Old machine tools like lathes were coated in a sort of thick filler ti hide all the casting imperfections and sand grain. If you strip this off you
may end up with a fairly rough looking finish.
Yep, I can confirm that stripping using a chemical stripper will soften and possibly remove any filler that has been used to hide casting defects.
This would also makes using a clear lacquer a non-starter since any filler would be very visible. I'd just finish it in the correct colour for
the lathe, using a hard wearing enamel paint or similar.
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v8kid
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| posted on 2/12/15 at 09:06 AM |
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Thanks Chaps, good comments, I'll strip it and see how it goes re the surface imperfections.
Other forums say that a special acidic stripper is required for aluminum any comments?
Cheers!
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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obfripper
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| posted on 2/12/15 at 02:48 PM |
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I've used biostrip on alloy wheels with no adverse effects, it's benzyl alcohol based and ph neutral so far safer than the old methylene
chloride.
It's pretty good on ordinary paint finishes, but needed multiple applications on powdercoat, with some elbow grease.
If you have the facilities, 1.5L 2K Clear Etch Clearcoat Gloss Lacquer For Aluminium, Alloys &Steel Surfaces would be ideal
for your clearcoat.
If not, and you want a hard durable finish, there is also clear powdercoat that would be fine for cosmetic alloy panels, i would not use it for
structural items though, as the temps involved can affect the temper of the alloy.
As a cheaper diy option, you could use phosphoric acid or acidic alloy wheel cleaner to manually etch the alloy for a 1k/synthetic clearcoat, but you
may end up with a streaky/patchy/blackened finish depending on the alloy, the alloy wheel cleaner may be better for finish as it will have a small
amount of hydrochloric/hydrofluroic acids that will break down the smut, but will be more expensive to buy.
If you manually etch, you'll need to be quick between rinsing clean/drying and applying clearcoat to give the best adhesion, as the alloy will
'skin over' with oxide pretty quickly.
Dave
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David Jenkins
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| posted on 2/12/15 at 05:23 PM |
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A friend stripped and repainted his old Colchester Student lathe - not sure what he used to get the paint off, but there certainly was a filler
underneath on the cast pieces. He re-filled them using a thin coat car body filler, rubbed down in the usual way. It looked brand-new once
he'd repainted everything in grey.
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v8kid
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| posted on 3/12/15 at 08:23 AM |
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Excellent thanks Dave that's exactly the information I was looking for.
Cheers!
quote:
Originally posted by obfripper
I've used biostrip on alloy wheels with no adverse effects, it's benzyl alcohol based and ph neutral so far safer than the old methylene
chloride.
It's pretty good on ordinary paint finishes, but needed multiple applications on powdercoat, with some elbow grease.
If you have the facilities, 1.5L 2K Clear Etch Clearcoat Gloss Lacquer For Aluminium, Alloys &Steel Surfaces would be ideal
for your clearcoat.
If not, and you want a hard durable finish, there is also clear powdercoat that would be fine for cosmetic alloy panels, i would not use it for
structural items though, as the temps involved can affect the temper of the alloy.
As a cheaper diy option, you could use phosphoric acid or acidic alloy wheel cleaner to manually etch the alloy for a 1k/synthetic clearcoat, but you
may end up with a streaky/patchy/blackened finish depending on the alloy, the alloy wheel cleaner may be better for finish as it will have a small
amount of hydrochloric/hydrofluroic acids that will break down the smut, but will be more expensive to buy.
If you manually etch, you'll need to be quick between rinsing clean/drying and applying clearcoat to give the best adhesion, as the alloy will
'skin over' with oxide pretty quickly.
Dave
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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