Dissolution of metals utilizing an aqueous H.sub.2 SO.sub.4 -H.sub.2 O.sub.2 -polysulfide etchant

A method of metal dissolution which comprises contacting a metal with an aqueous solution containing from about 0.2 to about 4.5 gram moles per liter of sulfuric acid, from about 0.25 to about 8 gram moles per liter of hydrogen peroxide and a catalytically effective amount of a polysulfide compound additive having the general formula ##STR3## wherein R is a hydroxyl group, a carboxyl group, a sulfonic acid group or a sulfonic acid salt group, each X independently from each other can be hydrogen, hydroxyl or C.sub.1 -C.sub.4 alkyl, each Y independently from each other can be hydrogen, hydroxyl or C.sub.1 -C.sub.4 alkyl, m is an integer from 1 to 18, and n is an integer from 2 to 5.