Abstract

The manuscript investigates the use of cathodic protection -based strategies (e.g. sacrificial anodes) to prevent corrosion phenomena of two green (e.g. recycled) 43200 and 46400 Aluminum alloys. These materials are selected due to their high concentration of alloying elements (e.g. Si, Cu, Fe) that renders them as a representative example of the typical composition of secondary Aluminums. Voltammetry and zero resistance ammeter (ZRA)-based methods are used to: a) asses the protection capability of Zinc-based sacrificial anodes; and b) experimentally determine the amount of Zinc required to cathodically protect a certain surface area of each investigated material for a specific period of time. As a further level of analysis, the manuscript investigates the protection capability of sacrificial anodes when coupled with an anodized secondary alloy. It is demonstrated that, in the case of highly alloyed Aluminums, cathodic protection can provide competing advantages with respect to conventional anodization treatments.

Introduction

In the recent years, the reduction of the environmental footprint of industrial processes is gaining momentum, targeting the carbon neutrality.1 This also involves Aluminum industry, in which the use of secondary (e.g. recycled) alloys is a possible solution in order to decrease the greenhouse gases (GHG) emissions.2 Indeed, raw materials produced starting from secondary Aluminum show GHG emission values up to one order of magnitude lower with respect to their primary equivalents.3

When referring to corrosion resistance, Aluminums are usually unsuitable for most of the industrial applications and anodization is often required.4,5,6,7,8 Nevertheless, secondary alloys, which typically include a high concentration of Silicon, Copper, Magnesium and Iron, are particularly challenging to be anodized, especially using conventional processes.9,10 At a first approximation, this can be associated with the presence of intermetallic precipitates within the Al matrix which generate microgalvanic coupling events and associated inhomogeneous anodic layers.11,12,13 In this context, the use of cathodic-protection-based strategies (e.g. sacrificial anodes) appears as an interesting possibility in order to increase the corrosion resistance of green Al alloys.

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