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!

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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Originally posted by mark chandler

For painting forget laquer, upol acid etch and silver paint.

[Edited on 1/12/15 by mark chandler]

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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.

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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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.

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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!

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

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.

Excellent thanks Dave that's exactly the information I was looking for.

Cheers!

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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

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