A most unusual metal

Being rather intrigued by Ian's findings ... I searched for relevant patents, and found this:

**LINK**

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=2672681A&KC=A&FT=D&ND=&date=19540323&DB=&locale=

... But I don't think that process would qualify as easy soldering with ordinary 60/40

Pehaps Ian's quickness of hand left the surface sufficiently free of oxides that the solder adequately wetted the surface without the use of benzoic acid.

MichaelG.

Could it possibly be pure tin?

easy to wet ..low melting point..silver in colour..

does it shriek?

Backshells are usually die cast zinc overplated with nickel when they are not metalised plastic. Zinc solders easily.

regards Martin

Last night I filed through the plated surface (definitely plated because there is layer of copper) and exposed the base material. Later today I will see how easily it tins after being exposed for several hours.

The casting is what I would call finely detailed, its mostly about 0.30mm thick yet where the two edges of the clamshell meet there is a male/female stepped joint.

I dismissed the idea of it being Tin because of the cost, also they would not have needed to plate the surface.

All in all a bit of a mystery.

Ian P

As I said, Zinc.

Martin

I read the first page and was going to say 'surely it's just zinc'... but I won't bother now.

Neil

"Could I just say it's zinc?".

. . . . . . "No sorry there isn't time"

(on loan from Monty Python)

I never thought in might be plain Zinc. Not that I know much about Zinc other than its used in galvanising but I thought it was very soft whereas this is hard and brittle (it is a cast part though).

Oddly in some previous replies Zinc is not perceived as being easily solderable.

Again odd is the fact that it is plated, as its is easily soldered and never ever going to be seen, why bother to plate it.

Ian P

Have a look at this data sheet

**LINK**

It's plated to look nice and shiny. Zinc is used for sacrificial anodes on canal craft and is similar to aluminium regarding softness, gets quite malleable if heated to 200 deg C and solders easily as you discovered.

regards Martin

Well I never!

I've been involved with electronics for too long and yet never been aware that straight Zinc was used for mechanical parts like these. This one is obviously Zinc so wood and trees come to mind.

Thanks

IanP

We used to have a zinc can opener, much bulkier than a pressed steel one.

I think it's in one of my scrap boxes... hmm I may have a use for it...

This might be the same crap that SU carburettors are made of. I tried TIG welding one and got large quantities of blue smoke, a sign of zinc.

Vintage car ali castings are full of zinc due to it being cheaper than ali and you can add it to molten ali to bulk it out

.

Martin,

I bow to your wisdom, but I remain absolutely astonished that die-cast Zinc [whether pure, or an alloy] can provide sufficient structural integrity for the shell in question:

[quote] The casting is what I would call finely detailed, its mostly about 0.30mm thick yet where the two edges of the clamshell meet there is a male/female stepped joint. [/quote]

MichaelG.

.

P.S. ... This is the best statement I can find on the matter of wall-thickness:

Wall Thickness
Zinc alloys have excellent casting properties, which means that thin walled cross-sections are possible. Zinc diecastings are often cast to a thickness of 1mm, with thinner sections possible depending on the flow of material to that area. Thin walled casting has a superior strength to weight ratio, thus strong and light zinc diecastings can be designed using the minimum of metal. This also improves the production rate and lowers cost.

**LINK** http://www.pmsdiecasting.co.uk/technical/for-designers/

Gosh this is going on and on. When corgi and dinky and matchbox cars started being made out of plastic all the muck metal had to be used for something

Fair comment, Bazyle

... But 0.3mm wall thickness is very impressive.

MichaelG.

I've got a tin can opener !

The other interesting thing about zinc is it screams when you bend it cold.

regards Martin

So do I

Russell