Restoring and repainting rusty tinplate

[Bassettblowke]

In the world of Die-cast restoration caustic soda finds frequent use and I use it on tinplate as well. I have always found Nitromors hard work even the old stuff although the stuff with the consistency of water for me worked better than the paste. The modern nitromors is a completely different product as far I can tell sharing only the brand name with the former highly noxious product.

Over the years I’ve heard many recommendations for all sort of odd concoctions. Car brake fluid once the favoured choice of vandals among them, personally I will stick to occasionally  drinking Coke and putting Vinegar on my chips there are more effective tried and tested methods out there.

[Il Grifone]

Coke still contains phosphoric acid, but it doesn't seem to have the same 'bite' it once did so there is probably less of it.

The last 'alleged' paint stripper I bought was b****y useless. It possibly wasn't Nitromors (DIY store own brand IIRC).

[009 micro modeller]

On 19/07/2020 at 02:46, PatB said:

Having recently discovered the delights of Marx tinplate, on severely rusted items that require a complete strip and repaint, I've been using the vinegar bath technique. The items to be treated are dismantled and left in a covered bucket of cheap white vinegar for a week or two, being inspected and given a bit of a scrub with a toothbrush every few days. Paint comes off very quickly and easily, surface rust turns to a sort of mush and brushes away, and deeper rust is dealt with in stages as the brushing removes successive layers. Although it takes a little time, it's very safe (mind you, I'd recommend not using the vinegar on your chips afterwards), seems effective, and appears to be quite gentle on the underlying material. Even leaving pieces in the bath for 2-3 weeks, I haven't managed to remove anything but paint and rust. 

 

After removal from the bath, rinse thoroughly, dry quickly (I use a hairdryer on Martian heat-Ray setting) and get a coat of primer on immediately, as any bare steel will start to rust again, pretty much instantly. I've been using generic etch primer and aerosol acrylics from the local car accessory shop. One of the reasons I've gone for US equipment is that American railroads and toy manufacturers were most considerate by painting most of their locos in plain satin black so appropriate paint can be had almost anywhere. For UK stuff, depending on how close you want to get to original, other paint sources may be appropriate.

 

Do you ever get the black speckled effect left on the metal (as in my previous picture) or does it go down to bare metal? My test pieces are using cider vinegar as I haven’t got the bulk white vinegar yet, in case that makes any difference. Also I notice that you can buy specific ‘cleaning vinegar’ but is this likely to be too aggressive?

[PatB]

8 hours ago, 009 micro modeller said:

 

Do you ever get the black speckled effect left on the metal (as in my previous picture) or does it go down to bare metal? My test pieces are using cider vinegar as I haven’t got the bulk white vinegar yet, in case that makes any difference. Also I notice that you can buy specific ‘cleaning vinegar’ but is this likely to be too aggressive?

I've found that, where the rust has been deep enough to completely destroy any plating and the smooth steel surface beneath, I'm left with a black or grey matt surface. I assume the black is a layer of iron oxide and the grey an oxide free, bare steel surface. I make sure such areas get a good scrub when rinsing but I don't worry overmuch about them as either appears to take paint well. If it happened in the middle of a surface that was supposed to be uniformly glossy I suspect it would require some work with hi-build primer and wet and dry to get a suitable finish. However, for where I've encountered it (amongst the coal on a tender top for example) and the modest standards I seek to achieve, it hasn't been a problem. 

 

Cider vinegar should be fine. It seems to be the acid of choice for many of the folk in the US doing this sort of thing. For what it's worth, theirs is mostly labelled as 5% strength. Our labelling in Oz is a bit different so direct comparisons are difficult. I use the white stuff because I had a few litres and don't like it much as a foodstuff. When I need more it's very cheap. I suspect that cleaning vinegar is no more concentrated but simply hasn't gone through the certification process to be sold for human consumption. I may be wrong though.

 

I think the key with any rust removal substance is to try it and to keep an eye on what's going on. I would expect different substances, different grades and sources of tinplate, and differing ambient temperatures to all make a difference to the reactions taking place. Given my findings with parts spending 2-3 weeks in vinegar that shrivels my nostril hairs, I think it's unlikely that anything labelled as vinegar, rather than acetic/ethanoic acid, will dissolve anything overnight. 

 

Edit: I've attached a couple of photos of a Marx wedge tender that has had the vinegar bath treatment, after washing and repainting. As you can see in the first photo, there is a rough patch in the tender top where the rust was particularly severe. Ironically, the texture looks rather more like coal than the smooth pressed tin around it. A nominally smooth surface would require some filling and sanding for an acceptable finish. That's not the fault of the acid bath though. If the metal's disappeared, it's disappeared. No chemical treatment is going to bring it back.

 

I also chucked in a photo of the rear of the same tender. It still has its relatively delicate grab handle on the right (these are usually bent flat on playworn examples) but the one on the left is now missing. Half of it disappeared in the bath (again, prior to treatment, there was nothing left of the missing bit but rust) and the easiest option seemed to be amputation of the remains rather than repair.

 

For a running example which will not be examined closely, I find these issues to be acceptable. Others may not.

 

Edited August 12, 2020 by PatB

[Nearholmer]

Googling about this topic gave me this essay from a plagiarising website - it’s quite good!

 

https://www.ukessays.com/essays/biology/potential-of-vinegar-as-rust-stain-remover-biology-essay.php

 

BTW, the fancy cider vinegar we have in the cupboard has a lot of sediment In it (shake the bottle before use), so best go for cheap brands.

 

Anyone tried “non-brewed condiment”, which is what chip shop vinegar really is? It’s very cheap from cash and carry type places.

[PatB]

26 minutes ago, Nearholmer said:

BTW, the fancy cider vinegar we have in the cupboard has a lot of sediment In it (shake the bottle before use), so best go for cheap brands.

 

 

Yeah, but the extra sediment does give scope for sneaking it back into the bottle after use, without anyone noticing.  

 

I've no doubt non-brewed condiment will work. It smells and tastes of acetic acid, so that's probably what it is, just like vinegar. However, all the non-brewed condiment I've seen has been quite dark brown. Probably won't hurt the chemical properties, but it's going to be harder to check progress and probably needs more attention to detail when cleaning up and preparing for paint. Over here, I can get white vinegar from the supermarket at $1.20 (about 65p) for 2L, which lasts for ages unless you're doing industrial quantities of restoration, so I don't see a need to economise further.

Edited August 12, 2020 by PatB

[Nearholmer]

18 minutes ago, PatB said:

Yeah, but the extra sediment does give scope for sneaking it back into the bottle after use, without anyone noticing.  

 

You've got me worried now!

 

All that stuff in the bottom of the bottle might be from other members of the family using it to de-scale kettles and stuff like that.

[meil]

anyone tried Lemon Juice and salt?

[PatB]

2 minutes ago, meil said:

anyone tried Lemon Juice and salt?

 

I would expect lemon juice to work (or citric acid from a homebrew supplies outfit), but I'd be rather reluctant to allow salt, or anything else containing chloride ions, anywhere near any steel I wanted to keep rust free in the future.

[Nearholmer]

The other definitely safe "home brew" is molasses/black-treacle, watered down just far enough that it counts as a liquid rather than a sticky gloop.

 

That works by chelation, and is very effective and no slower than an acid-bath at the sort of concentrations in vinegar (4 to 5%).

 

It only deals with rust, leaving any paint/printing intact, so is quite good for stabilising things that have got the odd nibble of rust but are mainly sound, although it will deal with quite heavily rusted things too. It needs a "daily agitation" to get fresh solution onto the rusty bits, though.

[PatB]

5 minutes ago, Nearholmer said:

The other definitely safe "home brew" is molasses/black-treacle, watered down just far enough that it counts as a liquid rather than a sticky gloop.

 

That works by chelation, and is very effective and no slower than an acid-bath at the sort of concentrations in vinegar (4 to 5%).

 

It only deals with rust, leaving any paint/printing intact, so is quite good for stabilising things that have got the odd nibble of rust but are mainly sound, although it will deal with quite heavily rusted things too. It needs a "daily agitation" to get fresh solution onto the rusty bits, though.

Interesting that it leaves paint intact. Although I'm aware of the technique, I've never previously registered this particular property. I might give it a go on a Marx 897 loco I've recently acquired. I'd like to get the rust off it, but I don't want to remove the remaining, rather lovely, detailed litho, as I have no means of adequately reproducing it.

 

One caveat, though. I would assume the molasses will need washing off afterwards. Whilst I don't know what British tinplate manufacturers used, by way of paint, I have discovered, by painful experience, that at least some US tinplate uses water soluble paint. The tender pictured above lost almost all its paint to an initial wash in warm water, as did an equally rusty caboose from the same era, although, thank goodness, a matching gondola and boxcar suffered no similar ill effects.

[Nearholmer]

Ooh er!

 

The bits I’ve done using it were Bassett Lowke and Hornby, and in neither case did anything seem water soluble.
 

Hornby paint is ‘bombproof’ naked-on enamel.

 

With the BL ‘blood and custard’ coaches I’m never sure whether the main colour finish is paint or printing - it’s strange stuff that is susceptible to damage from excess warmth, but I don’t think it’s water-soluble. The black parts and the interior partition and double-skin (coffee coloured) are I think spray painted originally, before punching-out, but it’s really difficult to be sure. Precision Models, who made them for BL, used the same “tech” as was used to make camera body parts “In the old days” and it’s a bit of a mystery to me - I’ve got an old Voightlander folding camera that has Matt black innards made from precisely cut pieces of very hard, but very thin steel. Lost arts, I think.

[009 micro modeller]

So far the vinegar seems to be quite good at removing the paint as well (which I want to do as it isn’t really salvageable) but should I actually be removing the paint with white spirit/paint stripper or similar as I would normally do and then going to vinegar for the rust? Tempted to paint this on but soak the vinegar.

[DonB]

12 minutes ago, Nearholmer said:

Ooh er!

 

The black parts and the interior partition and double-skin (coffee coloured) are I think spray painted originally, before punching-out, but it’s really difficult to be sure. Precision Models, who made them for BL, used the same “tech” as was used to make camera body parts “In the old days” and it’s a bit of a mystery to me - I’ve got an old Voightlander folding camera that has Matt black innards made from precisely cut pieces of very hard, but very thin steel. Lost arts, I think.

 

Yes ! A "lost  art". During my working days I tried to replicate, (at the behest of a friend into the history of hand guns,) the similar finish but made lustrous by being polished, achieved by the makers of the Colt six-shooter. My belief is that it was performed by heating in an atmosphere of steam, but I was never very successful.

[PatB]

1 hour ago, 009 micro modeller said:

So far the vinegar seems to be quite good at removing the paint as well (which I want to do as it isn’t really salvageable) but should I actually be removing the paint with white spirit/paint stripper or similar as I would normally do and then going to vinegar for the rust? Tempted to paint this on but soak the vinegar.

I'd advise not bothering. Why add another operation/substance when you don't need to?

[009 micro modeller]

I’ve now established that the metal really will rust immediately after removal from the vinegar bath and rinsing. So is there a way to prevent one side rusting while painting the other? Otherwise I’m thinking of ways in which both sides can be painted simultaneously.

[Nearholmer]

I've had that trouble on de-greased steel sheet parts, and the weather currently is optimal to make it happen, warm with amazingly high humidity, but I'm not sure it actually matters that much. I've got a 16mm/ft battery-diesel that I built more than twenty years ago, where this happened. I primed straight over the haze of rust as it was forming, and the paint-work has survived without a blemish.

 

I hang things up to spray them, and go at all surfaces at once; our washing line bears witness to overspray from a bike frame!

[Bassettblowke]

In a previous life I had more experience of dealing with rust than I care to remember, a chipping hammer and a descaling pistol were never far from my hand And neither was a large pail of zinc chromate primer. It’s the nature of the beast that any ferrous metal will rust when exposed to the air, in the marine environment this is especially so hence the need to progress the job quickly. Many primers are porous so the top coat needs to be applied as quickly as possible. Care needs to taken to provide adequate coverage as it only takes one pin sized hole in the finish for rust to rapidly gain a foothold and spread beneath your nice pristine paint system. If you have stripped an item back to bare metal it really should be primed the same day and the finishing coats applied as soon as the primer has dried.
There really is no silver bullet when it comes to rust, nothing on Gods green earth will prevent ferrous metal returning to its natural state all you can do is slow that process or speed it up depending on your chosen method.

On the bright side the last time I handled Zinc Chromate was in the 70’s and to date despite the dire warnings Issued in subsequent years, I haven’t sprouted a second head, the lungs full of rust dust might come back to haunt me though, and the high as a kite paint fumes from working in confined spaces doesn’t bear thinking about either. The two pack epoxy deck paint was quick drying so you had to motor with the roller before the stuff went off in the bucket.

Thank God for the HSE and the abolition of Crown Immunity just a shame it isn’t retrospective.

Edited August 13, 2020 by Bassettblowke

[PatB]

The generic etch primer I use claims to be anti-rust on the tin, which makes me suspect it has some zinc in it. I just waft it on over whatever is left after rinsing and drying and it seems to stay put pretty well, with nothing coming through. I do live in a slightly less conducive to rust climate than the UK though. Mind you, when it does rain here, it really gets on with it and, because it's rarely particularly cold, we can see very high humidity during wet spells.

[Bassettblowke]

I wouldn’t worry to much about exposure to any paint primer the only caveat being you observe sensible precautions. Problems mainly arise in industry where the likes of red lead, white lead, calcium plumbate, zinc phosphate and zinc chromate were used in vast quantities within manufacturing processes. For the hobbyist Removing rather than applying them probably carries more risk.

modern etch primer is wonderful stuff although the high build nature of the paint can sometimes be an issue.

The cleaner the surface the better, most rust treatments don’t remove rust or convert it all they do is seal it and give you a suitable surface to paint, I would suggest abrasion is the best option wherever possible, total rust removal being the aim. Obviously this isn’t always achievable And that’s where all these rust treatments find a niche. 
When looking at many of these products Hammerite, Jenolite, Waxoyl and numerous others many lay claim to use in industry and the MOD I can say hand on heart I never once encountered any of them. The only exception was Rocket WD40 which was embraced big time although this was a water displacement product it rapidly came to be used for all manner of oddball things. Rumour had it that the engineers writer brushed his teeth with it.
The Navy in particular didn’t look kindly on the quack remedy school of thought, any deviation from the accepted process would undoubtedly bring down the wrath of the Buffer and even worse the Jimmy neither in any incarnation inclined to give anything the benefit of the doubt.

Once you have a suitable surface for paint it must be applied promptly and properly, no point in doing a thorough job on rust removal if you skimp on the paint system.

Rust like dry rot is quite content to fester out of sight even underneath what might appear to be a sound surface, An elderly frigate that was dispatched to the Far East along with my own ship was alongside in Simonstown South Africa for an assisted maintenance period and investigation of a leak on her focsle deck, by the time they were finished the investigation one of her deck plates resembled a lace curtain, this was cut out and replaced. In reality  the whole ship was unfit for service and whoever thought it suitable for service in the Far East obviously needed their head testing. On return it was promptly scrapped.