Corrosion Sensor Development for Condition-Based Maintenance of Aircraft

Gino Rinaldi,Les Lebrun,Heping Ding,Trisha Huber,Heather McIntosh,John Weber

doi:10.1155/2012/684024

Abstract

Aircraft routinely operate in atmospheric environments that, over time, will impact their structural integrity. Material protection and selection schemes notwithstanding, recurrent exposure to chlorides, pollution, temperature gradients, and moisture provide the necessary electrochemical conditions for the development and profusion of corrosion in aircraft structures. For aircraft operators, this becomes an important safety matter as corrosion found in a given aircraft must be assumed to be present in all of that type of aircraft. This safety protocol and its associated unscheduled maintenance requirement drive up the operational costs of the fleet and limit the availability of the aircraft. Hence, there is an opportunity at present for developing novel sensing technologies and schemes to aid in shifting time-based maintenance schedules towards condition-based maintenance procedures. In this work, part of the ongoing development of a multiparameter integrated corrosion sensor is presented. It consists of carbon nanotube/polyaniline polymer sensors and commercial-off-the-shelf sensors. It is being developed primarily for monitoring environmental and material factors for the purpose of providing a means to more accurately assess the structural integrity of aerospace aluminium alloys through fusion of multiparameter sensor data. Preliminary experimental test results are presented for chloride ion concentration, hydrogen gas evolution, humidity variations, and material degradation.

Highlights

Metals are vulnerable to corrosion due to environmental factors, and in the majority of cases engineering-grade metals and alloys are selected based on design and functionality priorities: strength, light-weight, mechanical and electrical properties, and so forth, rather than corrosion resistance per se [1]
The polyaniline [25] (PANI)/camphor sulfonic acid (CSA)-based sensors developed for hydrogen sensing were tested in a dry hydrogen/argon atmosphere
The sensor output increased by 15 mV over the measuring span, which corresponds to ∼3% hydrogen (7.5 mL) within the glass container, which in turn indicates that approximately 6 mg of aluminium was consumed

Summary

Introduction

Metals are vulnerable to corrosion due to environmental factors, and in the majority of cases engineering-grade metals and alloys are selected based on design and functionality priorities: strength, light-weight, mechanical and electrical properties, and so forth, rather than corrosion resistance per se [1]. The cost of corrosion has a substantial impact on the economies of all nations with the United States spending approximately $437 billion annually for corroded infrastructure maintenance and replacement [2] This costing trend is increasing because aircraft are exposed to service operating environments that negatively impact their long-term durability. A serious result of undetected corrosion is that it can have a cascading effect by which it can precipitate and accelerate fatigue damage [5] leading to a corresponding decrease in the load bearing capacity for that structure In this respect, the structural integrity of the aircraft is undermined by two separate yet complicit factors.

Aluminium Corrosion Chemistry in Aqueous Solution

Hydrogen Gas and Humidity Sensing Nodes

Experimental Section

Experimental Results

Conclusions