Now a question-- would you still avoid all copper-based alloys
if the ring is to be lined with silver or gold?
The question I have though is what if you lined the ring? Would
the shakudo (or even copper for that matter) stand up to years of
use (and possibly misuse) if they were external to the ring with a
gold or silver liner?
Yes copper alloys like shakudo, shibuichi, brass, bronze will all
corrode even if there is a liner of precious or corrosion resistant
(stainless steel or titanium) metal . In fact it is the presence of
the additional metals that cause the rapid corrosion of the copper
alloys. There is a galvanic “cell” set up when ever two metals are
in contact with each other and in the presence of an electrolyte
like salt water (sweat) the one with the greatest "anodic potential"
will corrode away while the one with the most "cathodic potential"
will be unaffected. The rate of corrosion will depend on lots of
factors but copper alloys paired with precious metals will all
corrode fairly rapidly under the conditions present on the human
hand i.e. warm, salty, and damp.
Here is a brief list of metals and their relative galvanic
potential. With any two (or more) metals in contact with each other
the one that is higher on the list will corrode. Some metals have
such noble properties that they will not corrode to any significant
degree like if you paired gold and platinum you would not see any
corrosion of the gold even though it is higher on the series than
platinum. In general the greater the separation of metals in the
list the greater the corrosion rate.
Corroded end (anodic, or least noble)
Galvanized steel or galvanized wrought iron
Copper alloy C28000 (Muntz metal, 60% Cu)
Copper alloy C67500 (manganese bronze A)
Copper alloys C46400, C46500, C46600, C46700 (naval brass)
Copper alloy C27000 (yellow brass, 65% Cu)
Copper alloys C44300, C44400, C44500 (admiralty brass)
Copper alloys C60800, C61400 (aluminum bronze)
Copper alloy C23000 (red brass, 85% Cu)
Copper C11000 (ETP copper)
Copper alloys C65100, C65500 (silicon bronze)
Copper alloy C71500 (copper nickel, 30% Ni)
Copper alloy C92300, cast (leaded tin bronze G)
Copper alloy C92200, cast (leaded tin bronze M)
Type 410 stainless steel (passive)
Type 304 stainless steel (passive)
Type 316 stainless steel (passive)
Protected end (cathodic, or most noble)
James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160
Member of the Better Business Bureau