Corrosion product formation sequence on Cu‐rich amalgams in various solutions

A single particle and four blended Cu‐rich amalgam systems were immersed in 37 °C solutions for 1–20 months in order to determine the characterization and sequence of corrosion product formation. X‐ray diffraction and SEM/EDS were used to characterize the products. The same sequence of formation occurred in all systems in Ringer's and 0.1% Ringer's solutions. The times at which each product formed varied with the brand of the amalgam and the concentration of the solution. The initial products were ZnSn(OH)₆ in Zn‐containing systems and SnO₂ in most other systems. Cu₂O formed next, followed by CuCl₂·3Cu(OH)₂. Immersion in 1% Na₂S yielded only HgS on all brands. A combination of 1% Na₂S and Ringer's solution yielded CaSn(OH)₆ after 2 months and Cu₂O at later periods. Artificial saliva resulted in a retardation of corrosion product formation and only limited amounts of a Sn‐rich product could be found after 20 months. Interactions of the various components appear to alter the nature and rate of corrosion product formation on these systems and additional systematic investigations are necessary to understand the influence of these interactions on corrosion.