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Old 20th Feb 2019, 1:52 pm   #1
Sparky67
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Default Cadmium(?) Plating Degradation

Hi all,

I have been given a non-working Racal RA1772 to look at by a friend. When it arrived I noticed the side and rear casings look like they have been in a damp environment and are quite badly corroded.The top and bottom covers are still clean and tidy. I am aware cadmium and its oxide is highly toxic so it has been put ‘out of the way’ while I find out more info.

So, two questions!

Is it likely / certain that the outer chassis casing of this Rx is cadmium plated?

If so is there any safe way to deal with it by spray-sealing or chemical removal perhaps?

If the answers to the above are yes and no I’m going to have to consider scrapping it ☹️

Thanks

Martin
G4NCE
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Old 20th Feb 2019, 2:19 pm   #2
The Philpott
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Default Re: Cadmium(?) Plating Degradation

Cd plating was a favoured method for a long time- from before WWII up to the mid eighties i would say.

Just oil it before you use any abrasion on it, surely- so nothing becomes airborne..? After wiping over with rag the remaining oil film protects.
Personally I have never scrapped anything just because it was Cd plated- it never even crossed my mind to do so.

Cad plating can appear greyish like aged zinc, but if passivated it will have a rainbow tint varying from pink-gold-green. When it deteriorates it turns to a white powder, this crumbles off and then or course,the steel underneath rusts.

Dave
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Old 20th Feb 2019, 2:23 pm   #3
Argus25
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Default Re: Cadmium(?) Plating Degradation

There is no need to worry about cadmium plating unless you propose to grind it off the metal surfaces and put it in your jam sandwich.

Just because something has an unpopular metal on it, like lead, mercury or cadmium, doesn't mean it is dangerous unless you go out of your way to imbibe it deliberately.

The metals themselves are not all that toxic, usually to get any decent toxicity it requires they are in organic salt complex form.

I wouldn't even bother putting on gloves to clean up a corroded cadmium chassis, I'd just clean them up like I have always done for the last 50 years. But if you want to put on a helmet and space suit, go ahead, there is no harm in that.

Cadmium became unpopular because it is not wonderful in large quantities for the environment. Most electroplaters, who worked with it all their lives had little issues with it. The greens hate it. It is a fantastic coating to prevent rust and corrosion, much better than zinc, I'm sorry it has largely gone due to to over zealous activities of "activists"
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Old 20th Feb 2019, 3:37 pm   #4
VT FUSE
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Default Re: Cadmium(?) Plating Degradation

Hear hear!

Way worse is the person that I know of who bought pallet fulls of old Clansman 24V NiCd batteries on eBay and found them to be useless scrap that would not charge, whereupon he bundled them onto his rural garden in a deteriorating heap,split cases and all.

Of course I informed him of the hazard they would present long term if not properly bagged and disposed of via the recycling centre just 3/4 of a mile away.
My advice was ignored and I continued to try to get him to act but alas he did nothing and any amount of trying to talk around all the environmental impacts long and short term fell on deaf ears.

We are no longer on speaking terms.



Mike
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Old 21st Feb 2019, 2:35 pm   #5
Maarten
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Default Re: Cadmium(?) Plating Degradation

In such a case, I'd just dig them up and take them away, if possible.

While the worst effects are long term environmental so having it on a chassis isn't a problem, cadmium is in fact also acutely toxic and doses can build up (so people who handle it industrially are more likely to be affected at some point in their lives, though it is said that the electroplating process itself is reasonably safe). Both if breathed in and ingested. Acute problems (an impressive list of them) are more likely when you're somewhat calcium, zinc, iron or protein deficient as cadmium may take their place and won't function as well as the original. Problems are less likely if you have a healthy intake of the above and copper, manganese, vitamins C and D.

Putting it on a jelly sandwich is definitely a bad idea, but I'd also scrape and sand it only when using protection against breathing in the dust, and wash my hands before eating anything.

Last edited by Maarten; 21st Feb 2019 at 2:40 pm.
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Old 21st Feb 2019, 4:43 pm   #6
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Default Re: Cadmium(?) Plating Degradation

It's like a lot of nasty substances - the infrequent occasional contact won't hurt.

By the time I've handled enough cad-plated steelwork to build up enough dose to affect me, I'll be long dead from other things.

But for people who work with it, day in, day out, life-changing amounts can accumulate well within a lifetime unless extra care is taken. And the environmental issues are not good, they'll be left behind for other generations. Better to leave cadmium ores where they can't hurt - in the ground - and only use cadmium where strictly necessary.
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Old 21st Feb 2019, 5:45 pm   #7
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Default Re: Cadmium(?) Plating Degradation

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Originally Posted by VT FUSE View Post
Way worse is the person that I know of who bought pallet fulls of old Clansman 24V NiCd batteries on eBay and found them to be useless scrap that would not charge, whereupon he bundled them onto his rural garden in a deteriorating heap,split cases and all.

Of course I informed him of the hazard they would present long term if not properly bagged and disposed of via the recycling centre just 3/4 of a mile away.
My advice was ignored and I continued to try to get him to act but alas he did nothing and any amount of trying to talk around all the environmental impacts long and short term fell on deaf ears.
Unfortunately, it's cases like this that mean that legislation (when finally introduced) is often stringent, inflexible and all-encompassing, in that it has to cater for the lowest common denominator in human behaviour. Most people are responsible about most things most of the time- but it's the few that spoil it for many.

Who knows who might subsequently innocently purchase his house and surrounding land and maybe grow vegetables on it that their children might eat? There's an unfortunate quirk of plant biology that they actually concentrate soil-sourced heavy metals in their tissues.

Last edited by turretslug; 21st Feb 2019 at 5:51 pm.
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Old 22nd Feb 2019, 4:15 am   #8
Bazz4CQJ
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Default Re: Cadmium(?) Plating Degradation

I think that a major reason why cadmium and various other metals came under tight restrictions was simply that their industrial use meant that unacceptable levels were being discharged in to the environment. Platers were 'disposing' of used solutions with no regard for the effects. Many of us on this forum will remember a time when very many British rivers and canals were badly polluted and generally quite dead and the recovery of the waterways in this country is something to be marvelled at.

In terms of handling a plated chassis, I'd wear some gloves and wipe it over with a damp cloth, and when dry, possibly wipe it over again with some thing like WD40 or some thin oil.

B
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Old 22nd Feb 2019, 11:07 am   #9
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Default Re: Cadmium(?) Plating Degradation

Agree, cadmium is highly toxic and the risks to workers routinely handling it in say an electroplating works were significant, as were the risks of disposal.

However the risks in handling an existing cadmium plated article are negligible.
I would suggest that basic precautions including working outside, wearing a dust mask, laundering clothing afterwards, and thorough handwashing before eating, should be taken if abrading or disturbing the plating in any way.

However normal handling in use would not worry me.
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Old 22nd Feb 2019, 11:36 am   #10
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Default Re: Cadmium(?) Plating Degradation

Thanks all.

Just to clarify it's not the bright cadmium plating I'm concerned about. I have handled a lot of that over the years...and probably drilled and sawed through it without even thinking about PPE or any possible adverse health effects in those days.

It's the larger areas of brown and white powdery deposits where the chassis has corroded on this Rx and which need cleaning up which took my interest. I read about the potential health effects of cadmium oxide, dust and fume at various sources on the internet, some of it involving minute amounts, which got my attention. It is understanding and scaling the difference between one-off and workers' exposure, which the studies appear to be more aimed at, which I'm not too sure about...

I have been told HSE have a leaflet on the subject - INDG391.

Martin
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Old 22nd Feb 2019, 1:34 pm   #11
The Philpott
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Default Re: Cadmium(?) Plating Degradation

If you take basic precautions against inhalation/ingestion then you are insuring yourself against the possibility of you being one of the unfortunates who are more susceptible (or allergic) to a given toxin. Mercury in tooth amalgam being a classic example of variable susceptibility-most of us will hopefully not be compromised by it but you get the occasional bod whose body responds to it to the extent where it all has to be removed, and they have to then be chelated to flush it out.

Dave
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Old 24th Feb 2019, 7:08 pm   #12
John Caswell
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Default Re: Cadmium(?) Plating Degradation

I do feel there is some paranoia over a lot of these heavy metal platings and other things like asbestos.
Generally most of us just handle the item short term and the the unit is put away.
I am not saying don't take sensible precautions but do use a modicum of sense.
I service quite a lot of turntables and most of the metalwork is "Cad and pass"
The question always asked is "do I need the metalwork stripped and replated"
I usually ask in return is "Are you going to handle it all day and then lick your fingers?" Pretty well in every case the customer can see sense in the comment.
I suppose its down to the "They say ((cadmium) or fill in what you will here) is dangerous therefore I must not touch it etc. etc."
I wish I knew who the "They" are.

John

Last edited by John Caswell; 24th Feb 2019 at 7:09 pm. Reason: typo
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Old 24th Feb 2019, 10:58 pm   #13
Bazz4CQJ
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Default Re: Cadmium(?) Plating Degradation

"They" would generally be the HSE in this country and for as long as I can recall they have been publishing "EH40: Workplace exposure limits", containing the list of workplace exposure limits for use with the Control of Substances Hazardous to Health Regulations, and updated every couple of years. It can be downloaded free from the HSE website.

Of course in a workplace, EH40 is legally binding.

I assume that the limits set by EH40 are based on epidemiological studies, published in peer review journals, which assess acceptable limits.

During my working life, my experience was that, among professional chemists, no one had problems or objected to EH40.

All that said, at home, I occasionally use Wood's metal (rich in cadmium) as a low melting point solder.

B
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Old 26th Feb 2019, 9:45 am   #14
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Default Re: Cadmium(?) Plating Degradation

Thanks for the reference. From EH40 the short-term workspace exposure limit (WEL) for Cadmium Oxide (as a Cadmium compound) is 0.075mg per cubic metre of air. That's only 3x the max long-term workers' exposure level.

It’s by far one of the lowest levels among all the chemicals and their compounds on the list, and only a factor of 10 higher than Beryllium. I can’t even start to visualise the initial amount dispersed in my garage to stay below the WEL though. Can anyone suggest how much in volume is 3mg of CdO dust?
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Old 26th Feb 2019, 1:37 pm   #15
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Default Re: Cadmium(?) Plating Degradation

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Can anyone suggest how much in volume is 3mg of CdO dust?
I'd assume a density of about 3g/cc, thinking that most powders sink in water, but are less dense than iron filings (7.65g/cc).

So, 3mg will be 0.001cc, or 1 cubic millimetre. Roughly!
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Old 1st Mar 2019, 10:05 am   #16
Sparky67
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Default Re: Cadmium(?) Plating Degradation

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So, 3mg will be 0.001cc, or 1 cubic millimetre. Roughly!
Wow! That is, to me, such a minute amount that I wouldn't have considered it even worth thinking about in the volume of air inside my garage. But it appears to be enough to hit the short-term (15 minute) HSE exposure limit, even when evenly distributed.

If the damage to this chassis is Cadmium Oxide the volume needing removal would be much more than 1 cu mm. Assuming a 10 micron thickness and 500x200 mm area on each side plus the rear panel, maybe over 1000 times more... I'm thinking the dust would likely contain some (even more dangerous in the same volume) cadmium particles from the edges of the corrosion as well. Hmmm...

I looked at some dust/fume protection respirators in my local Machine Mart the other day. They stop 99.97%. If my maths is right that's 3/10000 getting through. Without oil to reduce the dust as suggested, the dust would be highly concentrated where it's being removed. Even a 99.97% reduction wouldn't be anywhere near enough to provide a safe environment to work in.

I never thought of corroded plating as an issue, but I am now seeing Cadmium in the same light as Beryllium. OK if intact. Highly dangerous if worked or damaged.

Thanks again for the advice.

Martin
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