Corrosion Control in the Aerospace Industry

Samuel Benavides

• Publisher: Woodhead Publishing
• Year: 2009
• ISBN:
  9781845695538
• Topic: Technology & Engineering
• Subtopic: Aeronautic & Astronautic Engineering
• Index: Technology & Engineering

Corrosion control in the aerospace industry has always been important, but is becoming more so with the ageing of the aircraft fleet. Corrosion control in the aerospace industry provides a comprehensive review of the subject with real-world perspectives and approaches to corrosion control and prevention.Part one discusses the fundamentals of corrosion and the cost of corrosion with chapters on such topics as corrosion and the threat to aircraft structural integrity and the effect of corrosion on aluminium alloys. Part two then reviews corrosion monitoring, evaluation and prediction including non-destructive evaluation of corrosion, integrated health and corrosion monitoring systems, modelling of corrosion and fatigue on aircraft structures and corrosion control in space launch vehicles. Finally, Part three covers corrosion protection and prevention, including chapters which discuss coating removal techniques, novel corrosion schemes, greases and their role in corrosion control and business strategies in fleet maintenance.With its distinguished editor and team of expert contributors, Corrosion control in the aerospace industry is a standard reference for everyone involved in the maintenance and daily operation of aircraft, as well as those concerned with aircraft safety, designers of aircraft, materials scientists and corrosion experts.

• Discusses the fundamentals of corrosion and the cost of corrosion to the aerospace industry
• Examines the threat corrosion poses to aircraft structural integrity and the effect of corrosion on the mechanical behaviour of aircraft
• Reviews methods for corrosion monitoring, evaluation and prediction examining both current practices and future trends

1

Corrosion in the aerospace industry

S. Benavides US Coast Guard Aging Aircraft Branch, USA

Abstract

This chapter serves as an introduction to the rest of the book, which is a conduit for moving beyond the basics of standard corrosion principles to a real-world perspective of aerospace corrosion, prediction and prevention. A holistic approach to corrosion sustainment processes is presented and alternative methods to modeling corrosion growth are discussed. Experts provide insight into cutting-edge knowledge of the complex variables that combine to influence the corrosion that poses such a threat to the aging fleets of aircraft. The importance of accurate corrosion prediction models, health monitoring systems, novel inspection methods for aircraft maintenance, and cradle-to-grave corrosion management in order to continue to fly safely is stressed.

Key words

corrosion modeling

aerospace industry

aircraft maintenance

1.1 Introduction

Commercial and military aircraft fleets are aging. Aircraft designers and manufacturers never suspected many of their air vehicles would be flying beyond their designed life (Fig. 1.1). As aircraft become older, they are subject to the insidious time-dependent effects of corrosion. Forgotten, ignored and often deferred, corrosion eventually threatens the integrity of aircraft structure. Traditional approaches to understanding the effects of aircraft corrosion have relied on the classic textbook models of general corrosion. However, the multifarious variables involved in aircraft corrosion are convoluted, complex and interacting. This chapter shows how this book is a conduit for moving beyond the basics of standard corrosion principles to a real-world perspective of aerospace corrosion, prediction and prevention.

1.1 A Dassault Falcon jet undergoing corrosion inspection and repair. Manufactured in 1983 and designed as a corporate business jet, this aircraft flies low-altitude maritime search-and-rescue missions in a corrosive marine environment. The aircraft is scheduled to retire in 2021.

An understanding of aerospace corrosion should account for the disparate confounding variables that influence corrosion. These variables include the interacting material properties that work in conjunction with one another such as fatigue strength and load carrying capability, both of which are compromised in the presence of corrosion. Coating protection systems designed to prevent corrosion can also vary. A fleet of aircraft may have an array of surface conversion coatings, primers, topcoats and corrosion preventative compounds, some of which may be traditional chromate-based while others are environmentally friendly. Of course, as long as the protection system functions, corrosion will not occur. However, an exceptionally unknown variable is the time at which corrosion begins. Determining the onset of corrosion has implications on the corrosion growth-rate, structural viability, inspection intervals, repair schedules and the remaining life of the structure. Finally, aircraft move from one location to another changing the environmental severity that effects corrosion. Variables such as humidity, sheltering, chloride levels, pollutants and distance from water also influence aircraft corrosion (Fig. 1.2).

1.2 Corroded aircraft skin resulting from the failure of the coating protection system. The onset of corrosion occurred when the primer and surface conversion coating no longer prevented electrolytes from reacting on the metallic substrate.

1.2 Aerospace corrosion

Corrosion compromises the properties of aircraft structure carrying people and cargo. In the event of a failure due to corrosion, the consequences can be catastrophic. This was brought to light by Aloha Airline’s Flight 243 that suffered an explosive decompression in 1988 as a result of metal fatigue exacerbated by corrosion. This watershed event, in which an airline attendant was swept from the cabin at 24 000 feet, established US civil and military programs of aging aircraft of which corrosion was a principal area of focus.¹ Although corrosion inspections on the Aloha Airlines class of 737 s were proposed by a Boeing alert service bulletin, no one predicted the apocalyptic damage from accelerated corrosion that would result from operating in the severe Hawaiian environment.² Since this mishap, the aviation community has struggled to accurately predict the onset of corrosion or the extent of structural damage it induces. Despite advances in corrosion algorithms, computation material research, simulation, reliability and maintenance data analysis, a reliable model for predicting corrosion on aging aircraft has yet to be produced. This book presents holistic approaches to corrosion sustainment processes and discusses alternative methods to modeling corrosion growth.

1.2.1 Corrosion and structural integrity

In the preliminary design of an aircraft, requirements such as weight, aerodynamics, fuel efficiency and other specifications are determined. Unfortunately, not all the requirements are attainable and compromises to the design and production of an aircraft result. Historically, corrosion prevention has not been appreciably designed into an aircraft. Dissimilar metals, lack of drain paths and po...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• Contributor contact details
• 1: Corrosion in the aerospace industry
• Part I: Corrosion fundamentals and cost of corrosion
• Part II: Corrosion monitoring, evaluation and prediction
• Part III: Corrosion protection and prevention
• Index