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MG Midget and Sprite Technical - Degreasant

Advice needed!
I need to clean and degrease some body panels prior to priming They have been undersealed, and also have been subject to oils, grease and wax.I can scrape the underseal off easily enough, but this still leaves a residue, together with the other oil -based contaminants.

The advice is NOT to use petrol, diesel, paraffin etc which all act as solvents, will spread the contaminating oils and will themselves leave oil deposits in the pores of the metal. The recommendation is to use a "caustic detergent", but I am not sure exactly what is meant by that. Is this the same as Caustic Soda - which is readily available and quite cheap, for unblocking drains?
Guy W

What about acetone..it removes oils easiel and does not leave a residue...active stuff in spay can break cleaner

1 Paper

trade bodyshop suppliers sell something called Panel Wipe, I think it's just cheap thinners-type fluid. And you could finish off with a Tak-cloth (same source).
David Smith

Brake cleaner may do it. Panel wipe doesn't really dissolve the underseal residue which is still left after scraping. Though l suspect this would mostly wipe off if heated with a torch first. But the point was really to remove the oils and greases without causing them to get driven into the pores of the metal. Prop's brake cleaner sounds a good idea.

But l still want to know what a caustic detergent is. I know that a detergent would emulsify the oils rather than dissolve them, but it needs to be powerful stuff to lift them off in the first place.
Guy W

Standard Celly thinners will get most things off and you can finish off with Panel Wipe.

If you look on the net, eg. Ebay, you can find Traffic film remover, which comes in caustic and non-caustic forms. I don't think the non-caustic type would touch underseal, but the caustic type is use to deep clean Lorries and Heavy Plant, so may work.

My choice would be the thinners and hand held wire brush after a gentle attack on the underseal with a twisted knot wire brush on a grinder.
Aerosol brake cleaner is very expensive.
Bernie Higginson

Thanks Bernie,
The bit I am struggling with is this concept of oily residues becoming impregnated in the pores of the metal and causing problems with later finishes. If this is an issue, then any product that dissolves the oil and grease is going to be a problem. Hence the use of an emulsifying detergent rather than a solvent such as thinners.

I am also looking for a cost effective and readily obtainable product - hence the question about drain cleaner (Sodium Hypochlorate) which is cheaply available from Asda. But a trip to the local motor factors also makes sense!

I see that specialists like Frost list stuff but I don't want to wait till half way through next week. And I really resent paying well over the odds for exotically named products are just standard industrial chemicals repackaged with fancy labels.

Bernie, to me, you are the expert on paints and painting so perhaps you have a view on this issue of oils impregnating the steel surface? It comes from the Rust.co.uk website where they also advise not to use angle grinder wire brushes etc before degreasing for the same reason.
Guy W

Guy
Can't comment on the paint removal but I can on the chemistry !

Sodium Hypochlorite is the active ingredient in bleach - it's actually slightly acidic - the opposite of caustic.

If you want something thats caustic then you want sodium hydroxide (Caustic Soda). - As you say you can typically get that for clearing drains but go careful with the powder, its a gloves and glasses job.

You'll usually find they get mixed together into things like drain unblocker (eg the Mr Muscle bottle I just poured down the kitchen sink) with a detergent (or 'non ionic surfactant on the label').

Finally one safety thing - never mix bleach (or hypochlorite) with a strong acid (like battery acid or the phosphoric acid in things like anti rust) - that'll generate Chlorine gas and that's fatal in enclosed spaces - and as it's heavier than air it tends to sit close to the ground

Have you thought about using nitromors paint stripper - I think that's a mixture of caustic with a solvent
timmyk

Tim,
That's great. Just the sort of chemistry help I needed as it is just far too many years since I did chemistry at school - and according to school reports I didn't do much there anyway!

So I was mixing up Hypochlorate with Hydroxide. It was Sodium Hydroxide that I was thinking would do it. Studying container labels this morning in the motor factors it is apparent that other than the use of the various Hazard Warning symbols, they are a bit cursory about the active ingredients. And you have to get hold of their COSH Data sheets to discover what they actually contain. They do identify Sodium Hydroxide as the principle ingredient in degreasing detergent, along with surficants which I understand.

Anyway, I have bought a 5L concentrate container of a generic degreasant that doesn't appear to include any solvent type stuff. Dilutes at 5:1 so I will try it as a dip. At £6.99 it is rather less than just the postage element of buying an expensive fancy label product on-line. We shall see how it performs.
Guy W

Well that was interesting. The degreasant worked well - all the grease and remnants of underseal came off quite easily. I had scraped it down thoroughly first. What was a surprise though is what I took to be brown staining from the underseal on the insides of the rear wings turns out to be an original factory applied brown paint.

This is a surprise as the car is, or at least was, originally green. But the brown is in a good state, well bonded to the steel and certainly is not a later addition over the original green. I can only assume that this was sprayed on in the factory before the rear wings or the complete rear body unit was welded into position.
Guy W

When I stripped all the underseal off my B, I found that the areas which weren't rusty were covered in the original brown factory primer. There was no trace of any paint, just primer covered with underseal.

I'm assuming that the underseal was applied at the factory, as it was also on the boot floor, above the petrol tank.

Dave O'Neill 2

Guy. You seem to have it sorted. I would still give a final wipe over with Panel Wipe just before you paint it,but use the two cloth method. ie. don't allow the panel wipe to dry by evaporation. Apply it with one cloth and get it off quickly with another dry clean lint free cloth. Then, as previously mentioned use a tack rag.

Stuff like Nitromors can be very difficult to completely get rid of, especially if you have scored the paint surface to help the process. It gets into the score lines and it can come back to haunt you further down the line by erupting through the paint. I have used it in the past, but I now try to stay away from it, not that I do a great deal of painting any more. Better to take a little longer and use a DA sander to get rid of layers of paint.

Tim's advice about phosphoric acid and bleach type liquids being mixed is invaluable, as people sometimes use stuff without being aware of the potential consequences. Like using 2k paint with the wrong (or no) respirator and using power tools to smooth off lead loaded areas. Lead dust in the air is very dangerous.
Bernie Higginson

Hi Dave, Yes that's the same brown primer that I have found. Where it is intact, it is surprisingly good for its age of 57 years. i.e not blistering or flaking. But in other areas the surface has pitted with rust spots.

The bits that I am currently working on are either difficult or impossible to see once the car is completed. So the aim isn't really to get a pristine paint finish, but to seal and protect areas that will be impossible to reach once this stage of the work is completed. I am preparing them for a coat of epoxy primer which should bond well to the inside of the wings and will provide a waterproof coating to protect from damp and condensation.
Guy W

Guy... i use spray on break cleaner allthe time for cleaning grease and grim off my stuff ...

What ive found there is no differance between the $7.00 branded cans and the $1.99 brand X store can..just make sure it can take a straw in the nozzle

Btw... this works awsome for starters that need to be clean and dry of oils and greases to work well and longivity...like on our 1275

But for a final clean up on the panals just a few clean cloths whip on / whip off mr miagee style witb acetone will remove an impurities before you do any priming and patching

You can get a qt or a gallon cheap from any house and home paint store...test it first on a small surfaces before appling all over

Prop
1 Paper

In the UK a good source of acetone is GRP materials suppliers, for example Allscot in Glasgow. Just look in yellow pages for your local fibreglass suppliers.

Cheers
Mike
M Wood

And Glassplies in Wigan for acetone
M Wood

being from the North East originally I'll support the local guys and gals at East Coast Fibreglass :-)

http://www.ecfibreglasssupplies.co.uk/p-1610-acetone.aspx
M McAndrew

This thread was discussed between 09/12/2016 and 11/12/2016

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