Use of Amperometric and Potentiometric Probes in Scanning Electrochemical Microscopy for the Spatially-Resolved Monitoring of Severe Localized Corrosion Sites on Aluminum Alloy 2098-T351.

Rejane M P Da Silva,Mariana X Milagre,Abenchara M Betancor-Abreu,Javier Izquierdo,Ricardo M Souto,Isolda Costa

doi:10.3390/s21041132

Abstract

Amperometric and potentiometric probes were employed for the detection and characterization of reactive sites on the 2098-T351 Al-alloy (AA2098-T351) using scanning electrochemical microscopy (SECM). Firstly, the probe of concept was performed on a model Mg-Al galvanic pair system using SECM in the amperometric and potentiometric operation modes, in order to address the responsiveness of the probes for the characterization of this galvanic pair system. Next, these sensing probes were employed to characterize the 2098-T351 alloy surface immersed in a saline aqueous solution at ambient temperature. The distribution of reactive sites and the local pH changes associated with severe localized corrosion (SLC) on the alloy surface were imaged and subsequently studied. Higher hydrogen evolution, lower oxygen depletion and acidification occurred at the SLC sites developed on the 2098-T351 Al-alloy.

Highlights

Published: 6 February 2021The 2098 aluminum alloy belongs to the third generation of Al-Li alloys
The amperometric and potentiometric scanning electrochemical microscopy (SECM) probes were used to characterize a Mg-Al galvanic pair immersed in naturally aerated NaCl solution, using a combination of amperometric and potentiometric operation modes in SECM
Amperometric and potentiometric SECM operations were initially performed on a model Mg-Al galvanic pair system in order to check the efficiency of these probes in the characterization of a galvanic pair system similar to that occurring in the spontaneously corroding 2098-T351 aluminum alloy

Summary

Introduction

Published: 6 February 2021The 2098 aluminum alloy belongs to the third generation of Al-Li alloys. The addition of Li to these new generation alloys aims to decrease the weight of aircrafts [2,3] These alloys are reported to have low density, good mechanical strength, and good toughness [4,5,6]. Al-Cu-Li alloys, such as 2098, present a reduction in Li content compared to previous first and second generation alloys [2,7], and this reduction causes greater toughness compared to alloys from previous generations [5,6]. This feature represents a significant advantage, since low toughness characteristics were a disadvantage in previous

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