Influence of the Solidification Defects on the Corrosion Resistance of Zamac 5 Obtained by Squeeze Casting

ABSTRACT Sanitary metals are objects that, according to the current requirements of the consumer market, must be both corrosion resistant and beautiful, with a shiny mirror appearance. These are usually produced in cast brass because of their easy processing and electrodeposition characteristics. However, to reduce production costs, brass has been replaced by zinc alloys in the manufacture of these components. Zamac has properties such as low melting point compared to brass, which allows the production of thin-walled parts and complex geometries. Pressure injection to obtain zinc hypoeutec alloys (Zamac 5) allows higher productivity associated with better dimensional characteristics, costing about 30% less than brass. This study presents the macro and microstructural characterization of Zamac 5 injected under pressure, relating them to the corrosion resistance of the alloy. For this, saline fog tests and analyzes were performed by scanning electron microscopy, microhardness tests and electrochemical corrosion tests. The Zamac 5 injected under pressure presented non-uniform corrosion in distinct regions of the part when subjected to the aggressive atmosphere. The results also showed that this fact is associated with porosity defects from the alloy manufacturing process. The microhardness of the alloy was also associated with defects from the manufacturing process. Finally, it was evidenced that the electrochemical behavior of the alloy is little influenced by the presence of the defects.