Structural characterisation and corrosion resistance of Ga-precious metal alloys formed by liquid-solid reaction at room temperature

An attempt to eliminate Kg from dental amalgams was made by substituting it with low melting Ga-based alloys, liquid at room temperature. However more information is needed on the influence of alloy composition and their ques tioned corrosion resistance. In this paper the reaction of some liquid ea a lloys and some solid precious metal alloys with different nobility was stud ied. Structural features, hardness and corrosion resistance of the obtained composite materials were investigated as a function of composition of the starting alloys? liquid/solid ratio and different mixing methods. Every com bination of the solid precious metal powders and the liquid Ga-alloys gives rise to similar composite materials, The structure always consists of unre acted solid alloy particles embedded in a complex matrix composed of many r eaction phases. The formation of some phases depends on the composition of the solid alley, others originate all the time; however their topography an d morphology may be different as well as their compositional range. The hig h porosity generally present in the composite materials markedly affects ha rdness values; nevertheless some prepared materials reach hardness comparab le with the one of commercial amalgams. The nobility of the solid alloy and porosity percentage play a determinant role on the corrosion behaviour. In all casts the low corrosion resistance of the experimented materials may b e attributed to a galvanic coupling between the reaction intermediate phase s and the unreacted liquid alloy remained inside the pores. (C) 2001 Elsevi er Science B.V. All lights reserved.