Evaluation of the electrochemical performance of Ag containing AAO layers after extended exposure to a model corrosive medium

Stephan V Kozhukharov,Denitsa Kiradzhiyska,Aleksander Tsanev,Christian Girginov,Georgy Avdeev

doi:10.5599/jese.820

Abstract

The coating procedure appears to be an indispensable finishing stage in the production of Al based industrial products, engineering facilities and equipment. For this reason, there is an ever-increasing interest towards the elaboration of reliable corrosion protective layers with apparent coverage, adhesion, and barrier properties. In this sense, both the formation of anodized aluminum oxide (AAO) layer and its further modification with silver enable the elaboration of advanced (Al-O-Ag) films with extended beneficial characteristics. The present research activities are aimed at the determination of the corrosion protective properties of electrochemically synthesized Al-O-Ag layers on the technically pure AA1050 alloy. The structures and compositions of the obtained Al-O-Ag layers were characterized by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The research activities were accomplished by means of two independent electrochemical characterization methods: electrochemical impedance spectroscopy (EIS) and potentiodynamic scanning (PDS). The electrochemical measurements were performed after 24, 168 and 672 hours of exposure to 3.5 % NaCl solution used as a model corrosive medium (MCM), in order to determine the barrier properties and durability of the elaborated Al-O-Ag layers. The analysis of the obtained results has undoubtedly shown that the proposed electrochemical Al-O-Ag layer formation can successfully be used for the creation of self-standing layers with apparent corrosion protective properties. Besides, Al-O-Ag system can be used as a basis for development of efficient protective layers suitable for application in biologically contaminated media.

Highlights

The widest field of use of the low doped Al alloys, such as AA1050 is the packaging of various nutrition products and soft drinks [1,2,3,4]
At low angles, between 10 and 30 angular degrees, a more intensive noise signal was registered for anodized aluminum oxide (AAO) and Al-O-Ag layers, which was clearer in the former case (Figure 3)
The flatter noisy plateau in the case of Al-O-Ag layer compared to the one of the AAO layer, is probably related to the shielding of AAO pore walls and bottoms by rather thin films of Ag deposits. This explication seems more plausible than any suggestion related to alterations of the thickness of the basic porous AAO matrix, promoted by the electrochemical Al-O-Ag layer formation

Summary

Introduction

The widest field of use of the low doped Al alloys, such as AA1050 is the packaging of various nutrition products and soft drinks [1,2,3,4]. Reliable packaging requires additional surface protection of Al-based materials, prior to being in contact with whatever nutrition product. This requirement arises for prevention of Al-ions resorption from such packaging materials [5,6,7], which endangers human health [8,9]. Anodization is a simple and reliable method for the formation of highly-ordered and self-organized porous oxides [10,11,12,13,14] This method enables the formation of reliable, large-scale, protective oxide layers using relatively simple equipment. The resulting anodized aluminum oxide (AAO) possesses remarkable corrosion protective abilities after extended periods of exposure to model corrosive media [15,16]

Objectives

Results

Conclusion