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Old 29th Nov 2021, 10:10 pm   #1
radiozero
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Default Chassis coatings (generally and specific sets)

Because bare steel corrodes very readily, metal radio chassis made of steel are either painted or plated with a metal that resists corrosion. Can anyone speak with authority on the plating used on the chassis of my TRIO JR-500S? I guess tin, but that's just a guess. It's quite easy to solder to. Thank you. Rich

Last edited by radiozero; 29th Nov 2021 at 10:24 pm.
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Old 29th Nov 2021, 10:26 pm   #2
bigfathairyvika
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Default Re: Chassis coatings (generally and specific sets)

I can't speak with authority, but I would say that because tin plating of steel has been the way to provide some sort of corrosion proofing for many many years in not only radio cases but also tin cans and the like the Trio cases are more than likely tin plated.

Mark
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Old 29th Nov 2021, 10:34 pm   #3
wave solder
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Default Re: Chassis coatings (generally and specific sets)

Chassis were often Zinc or Cadmium plated to prevent corrosion.
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Old 29th Nov 2021, 10:42 pm   #4
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Default Re: Chassis coatings (generally and specific sets)

It used to be Cadmium, but thats very poisonous so no longer used. Today its Passivated Zinc Chromate. Zinc is not as good as Cadmium but much safer. Both have a "gold" look about them when in good condition. If your chassis is easy to solder I would suggest its neither. Are you sure its actually soldered? or just "stuck on " ? Normally a chassis requires one hellava soldering iron, like 150 to 200 watts, and requires some preparation work before it will solder properly.

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Old 29th Nov 2021, 10:51 pm   #5
radiozero
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Default Re: Chassis coatings (generally and specific sets)

Tags have been punched out from the chassis. And wires soldered to these tags.
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Old 29th Nov 2021, 11:08 pm   #6
joebog1
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Default Re: Chassis coatings (generally and specific sets)

Yes, I have seen that construction before. I think those tags are pre prepared before the set is actually constructed. Thet are pre tinned, and the coating may be ground/abraded away before soldering.
Steel will solder very well by itself if its cleaned and a decent flux used. For steel its generally "killed sprits" or Bakers fluid which is a comercially available product. In either case it is hydrochloric acid into which has been added enough zinc metal until the solution is saturated, i.e. when the reaction no longer occurs. After soldering or tinning the tags, the chassis/escutcheon is then washed to neutralize the flux as it remains fairly corrosive, especially in an electronics chassis.

This is just my experience in chassis/escutcheon preparation.

Joe
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Old 29th Nov 2021, 11:19 pm   #7
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Default Re: Chassis coatings (generally and specific sets)

Has it been vapour blasted?
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Old 30th Nov 2021, 12:00 am   #8
kalee20
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Default Re: Chassis coatings (generally and specific sets)

I've seen punched-out tags on steel chassis, they actually solder rather well with a modest soldering iron because steel is a pretty lousy conductor of heat - at least compared with copper.

As for the plating: I'd suspect zinc rather than tin. Both give good protection, but with tim if there's a scratch, the exposed steel corrodes faster due to electrochemical action. Whereas zinc, the coating either side corrodes sacrificially helping preserve the base metal.
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