Mr. Wizard
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Registered: 30-3-2003
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Recovering Platinum tips on spark-plugs
It was time for the 100K mile tune up on my truck, so I asked the mechanic to save the plugs, which had Platinum on the central electrode. Some plug
models have platinum on both electrodes, but mine only had it on one. I could clearly see the erosion of the metal on the ground electrode, which did
not have Platinum on it. The central electrodes are worn, but still have blobs of platinum on them after over 110K miles. I would guess that over half
the original Platinum is gone from the tips.
Getting the Platinum tips off was a bit harder than I anticipated. My first attempt in using a pair of wire cutters on the tip resulted in the bit of
metal shooting off into the unknown. The final procedure was to bend away the ground electrode, shatter the ceramic insulator around the central
electrode, then to hacksaw the electrode almost off. The small part almost cut off, was then grabbed by a pair of pliers and twisted off. I managed to
get 9 out of 10 with this method. The electrode was a copper rod, with some sort of gray metal sheath that ended with a blob of Platinum. I don't know
what the gray metal sheath is. I had to leave some of the copper and sheath on the tip, to make sure I got it all.
My plan is to dissolve the base metal sheath and electrode in some crude nitric acid, or sulfuric acid , leaving the Platinum buttons.
Any suggestions would be welcome.
The small dark picture shows an extreme close up of a tip. The lighter lens shaped object, with the black band to it's right, is the Platinum tip.
Sorry about the pictures, all were taken with a cell phone.
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Wizzard
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I believe, fellow Wizard, is that there is but an electroplated layer on there- Maybe not even worth the effort.
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Neil
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Registered: 19-3-2008
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Dissolve the whole thing in nitric, pour off the nitric and test it for platinum content.
Take the left overs that did not dissolve in nitric and treat with aqua regia, drop with ammonium chloride, incinerate....
Every time you start the car you lose a bit of Pt, Ru, and Pl out the tail pipe 
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