Corrosion behavior of primary and secondary AlSi high pressure die casting alloys

Abstract

This work characterized and compared the corrosion resistance of a traditional secondary HPDC AlSiCu alloy with two innovative AlSi low‐Cu and low‐Fe ones. Samples were collected from both the bulk and the skin of castings to evaluate the differences. Potentiodynamic tests were performed in 3.5% NaCl and 0.05 M Borax + 0.01 M NaCl water solutions and microstructural analyses have been carried out. The results demonstrated the higher corrosion resistance of the two innovative alloys tested. Skin surface showed a worse resistance compared to bulk, especially for the traditional AlSiCu alloy.

A study of a non‐conventional evaluation of results from salt spray test of aluminum High Pressure Die Casting alloys for automotive components

“…These two factors reduce respectively the effect of uneven distribution of porosity and intermetallics in the samples and the potential local and transient events that decrease the reliability of electrochemical analysis. Indeed, porosities and intermetallics, that are widely present in castings, exert a great contribution to the formation of local galvanic effects and are the main responsible for the pit formation, as already evidenced in previous works …”

“…As mentioned, the results of some of the electrochemical measurements reported in an authors’ previous work are summarized in the present section for comparison purposes. In particular, the comparison between the polarization curves of EN AC‐43500, EN AC‐44400, and EN AC‐46000 samples in 3.5 wt% NaCl solution is shown in Figure .…”

“…Nevertheless, this class of alloys exhibits a very low ductility, due to the formation of β‐phase (AlFeSi) precipitates, and consequently they cannot be used for heavier applications like safety relevant structural pieces. In addition, the corrosion resistance is strongly reduced by iron and copper precipitates . Recently, some innovative aluminum materials, called “structural alloys,” have been developed for the manufacturing of components that require high mechanical behavior.…”

“…In addition, the corrosion resistance is strongly reduced by iron and copper precipitates. [20] Recently, some innovative aluminum materials, called "structural alloys," have been developed for the manufacturing of components that require high mechanical behavior. In detail, AlSi9Mn alloys, one of the most employed structural alloy class, [21][22][23] differ from the traditional AlSi9Cux alloys for the lower level of iron (less than 0.5%), reduced in order to improve mechanical performances, the major amount of manganese (0.5-0.8%), that replaces the iron for the prevention of the die soldering, and the lower level of copper (below 0.2%) for a better corrosion resistance.…”

Role of Chemical Composition in Corrosion of Aluminum Alloys

“…The chemical composition leads to the formation of different microstructural features. From this point of view the most important features are α-matrix (dendrite cell size, secondary dendrite arm spacing-SDAS, grain size), eutectic silicon particles and intermetallic phases (size, morphology, amount) and porosity [3,4,6,7]. Osório et al [5,6] investigated that the dendrite fineness can be even of more importance in the mechanical properties compared to the effect of grain size.…”