Etchant to reveal platinum welds
Category: Physical Methods
Subject: Etchant to reveal platinum welds
What etchant can be used to reveal welds in platinum group metals?
Platinum, rhodium, iridium and alloys can be electrolytically etched in a 10% HCl solution saturated with NaCl.
AC current should be used through a platinum wire pin and platinum cathode. We use 2–3 volts and moderate the current appropriately for sample surface area to avoid burning; typically 0.4–1.2 amps should suffice; the bottom end for platinum and rhodium.
It will generally take several minutes and better results are obtained if the sample is etched, re-polished and re-etched.
Answer posted 09 May 2007
Submitted by: Ms Sara Coles
Affiliation: Platinum Metals Review
Answered by: Robert McGrath
Affiliation: Johnson Matthey Noble Metals