In my case the copper is in the form of appliques on the outer
surface, so presumably if the copper corrodes the structure of the
rings will not be compromised. However, they could end up looking
ugly. And of course if the silver starts getting eaten away. not
so good. But also, I'm guessing the fact that the copper is not
touching the skin and will not be directly exposed to sweat (unless
the wearer sweats profusely) would make some difference. Can anyone
comment on that point?
It is the mere presence of water in its liquid form that is the
culprit. With the exception of specially prepared lab grade water
all water is conductive. While the salts from sweat make it more
conductive speeding the reaction, skin contact is not necessary for
the galvanic corrosion to occur.
This same discussion has been posting to the metal clay yahoo forum
and your (Jim’s) experiment info was posted there as well. I have
been trying to answer questions about this on that forum, because
there are many on that forum who have been combining fine silver and
copper clays, and who, I believe, would experience similar problems
with copper erosion/etching resulting from the same galvanic
reaction.
I keep protesting that I am not a chemist and, although I’ve read
Jim’s article, my vocabulary re: chemistry is limited, a vocabulary
that is additionally limited by the many years that have passed
since my high school chemistry classes. Jim, if you’re reading this,
would you log on to the metal clay forum and explain in more detail
what your understanding of this process is. Thanks.
As an aside, we experienced this galvanic reaction when a copper
water pipe was touching the base of our iron bathtub. The end result
was a pinhole in the copper pipe and a collection of water above the
ceiling of our living room, followed by a gushing waterfall at 3:00
A. M. one morning. Case in point!
There are some applcations where this corrosion doesnt seem to take
place, for example we have here a Mercedes 190 some 24 yrs old, made
when engineers dictated the specs not the sales people, and all the
electrical connections are soldered then silver plated ie the plug
male into female sort.
No corrosion over this time.
Also Im wearing a cuff type bracelet I made for meself in 1976 18/8
stainless steel base with 9 ct red gold applique soldered onto the
stainless with Easyflo No1 on the face side.
also no corrosion.
Another alloy I use, tho its hard to find is cunifer 10. This is
used in marine applications for hot sea water trunking and heat
exchangers. I get it as 3in dia drawn seamless pipe some 90/1000 in
thick recovered from old ships.
I slit it length wise open up to make sheet 9in wide by 2 ft long.
Use it for all sorts of products, When I want it thinner I
guillotine it to width then anneal and roll down to thickness not by
hand tho!!. It fire oxidises to a lovely brown colour thats very hard
wearing. The IMI large folder from 1975 lists all the copper based
alloys available at that time with their specs and applications Very
useful.
Was wondering about the galvanic reactions, if there was a way to
put stainless between the different copper alloy layers, there might
be some joy that way.
Maybe the only problem would possibly be internal corrosion within
the individual alloys.
The biggest form of corrosion in silver solders (brazing alloys) is
the dezincification of the solder when the joint area comes into
contact with water, particularly salt water.
It is the mere presence of water in its liquid form that is the
culprit. With the exception of specially prepared lab grade water
all water is conductive. While the salts from sweat make it more
conductive speeding the reaction, skin contact is not necessary
for the galvanic corrosion to occur.
Also something people don’t consider is if you live near the sea.
Pretty much everything corrodes in the atmosphere. This may also
speed up the galvanic reactions in these beautiful objects.
When I was working in the Aluminium (aluminum) industry we were
regaled with many accounts of corrosion.
Copper was a nasty when it became wet. A man complained that his
aluminium dingy had holes in it. The problem was that he’d dropped
some bronze coins into the boat and they got wet, ate holes through
the boat in short order.
Aluminium will have a galvanic reaction with other metals on the
galvanic table, the severity of the reaction is usually governed by
the distance separation on that table. The only exception is
stainless steel and aluminium wont have a reaction, unless it’s in a
salt water environment.
If a neutral barrier was placed between the layers of metal in a
mokume gane ring, wouldn’t that reduce the problem?
Ted, You gave a couple of personal examples where association of
dissimilar metals did not result in corrosion. In order for
electrolitic corrosion to exist there must be an electrolite at the
point of contact between the two metals. In the examples you gave,
introduction of an electrolite is unlikely.
If a neutral barrier was placed between the layers of metal in a
mokume gane ring, wouldn't that reduce the problem?
Not if it is electrically conductive. So if you wanted to laminate
plastic between each layer you could have dielectrically isolated
metals and no galvanic corrosion but otherwise no dice.
Was wondering about the galvanic reactions, if there was a way to
put stainless between the different copper alloy layers, there
might be some joy that way.
No it would still result in the copper alloys going away.
There are some applcations where this corrosion doesnt seem to
take place, for example we have here a Mercedes 190 some 24 yrs
old, made when engineers dictated the specs not the sales people,
and all the electrical connections are soldered then silver plated
ie the plug male into female sort.
Water exposure is the key not much or not any water then little or
no corrosion
Also Im wearing a cuff type bracelet I made for meself in 1976
18/8 stainless steel base with 9 ct red gold applique soldered onto
the stainless with Easyflo No1 on the face side.
Stainless generates a passive film of chromium oxide on its surface,
that is what makes it stainless. As long as that film is not damaged
it will not corrode, however put it in the right environment and it
will definitely be subject to such corrosion. But your wrist is not
nearly a nasty enough environment to see this type of corrosion. But
in marine service 18/8 stainless is definitely subject to galvanic
corrosion.
Another alloy I use, tho its hard to find is cunifer 10. This is
used in marine applications for hot sea water trunking and heat
exchangers. I get it as 3in dia drawn seamless pipe some 90/1000
in thick recovered from old ships.
I slit it length wise open up to make sheet 9in wide by 2 ft long.
Use it for all sorts of products, When I want it thinner I
guillotine it to width then anneal and roll down to thickness not
by hand tho!!. It fire oxidises to a lovely brown colour thats very
hard wearing. The IMI large folder from 1975 lists all the copper
based alloys available at that time with their specs and
applications Very useful.
Through careful selection of materials you can greatly reduce the
likelihood of galvanic corrosion but that means engineering not
aesthetics or consumer desire dictates the material choices
There are some applcations where this corrosion doesnt seem to take
place, for example we have here a Mercedes 190 some 24 yrs old,
made when engineers dictated the specs not the sales people, and
all the electrical connections are soldered then silver plated ie
the plug male into female sort. No corrosion over this time. Also
Im wearing a cuff type bracelet I made for meself in 1976 18/8
stainless steel base with 9 ct red gold applique soldered onto the
stainless with Easyflo No1 on the face side. also no corrosion.
In a previous job I spent many hours recommending solders (brazing
alloys) for specific joining applications; you are correct, let the
engineers and not the accountants specify a job and generally things
last, not the built in obsolescence we have today.
Regarding the solder (brazing alloy) you used. Easyflo No 1 was 42%
silver alloy which contained cadmium. It was an excellent alloy for
metal joining and for most general purpose applications was highly
corrosion resistant. When the legislation was introduced restricting
cadmium in solders (brazing alloys) then you needed to use a 55%
cadmium free silver alloy to get the equivalent corrosion resistance
(Silverflo 55 from this manufacturer). Silverflo and Easyflo are the
trade names of brazing alloys (solders) manufactured by Johnson
Matthey. These two alloys are manufactured to European standards,
for those interested Easyflo No1 is EN1044 1999 AG301 and Silverflo
55 is EN1044 1999 AG 103; as they say other manufacturers are
available!
For marine environments the alloy recommended was the equivalent of
Matthey’s Argobraze 56; a 56% silver alloy with copper, indium and
nickel - importantly no zinc content as the zinc phase in the alloy
was the most susceptible to corrosion (also a European standard
alloy, EN 1044 1999 AG403).
For the record I have never worked for Johnson Matthey but their
trade names have become synonymous with certain solders (brazing
alloys) and that is why I have used them above.
Is there a problem with corrosion in shibuichi? When copper and
silver are melted and cast together, does the copper still erode?
Yes Silver and copper are a duplex alloy in most cases. That means
there are areas of silver rich grains and areas of coper rich
grains, Electrolysis will cause the copper rich areas to corrode. So
don’t use it for rings.
If a neutral barrier was placed between the layers of metal in a
mokume gane ring, wouldn't that reduce the problem? Not if it is
electrically conductive. So if you wanted to laminate plastic
between each layer you could have dielectrically isolated metals
and no galvanic corrosion but otherwise no dice.
That definitely sucks
Obviously the aluminium and stainless solution wouldn’t work here,
bugger
When in 1968 I started full time applied art metal work, I was
selling in London and was a regular visitor to Johnson Matthey in
Hatton Garden. they were very helpful and supplied me with all the
technical data I could wish for, on all their precious metal ranges
as well as all their brazing alloys.
I have their data here still.
so I use their brazing alloys exclusively.
Mainly EF 1 EF 2 and EF3. I hve several kilos of these brazing
alloys as well as the hall marking grades put by so will never need
to buy any more in my lifetime.
And yes EF 1 is the cadmium grade I have here, with proper
ventilation theres no problem.
thanksfor your background info.
Nice to hear that there are others that know of the older grade
metalalloys.
