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In the past, the RAF’s approach to corrosion was reactive: corrosion occurred, was identified and then rectified. Such a strategy is no longer acceptable, as corrosion rectification is costly both in terms of material and aircraft availability. More importantly, as escalating replacement costs force us to retain aircraft in service for ever‐longer periods, the threat posed to structural integrity by corrosion and repeated corrosion repairs can no longer be tolerated. Consequently, the RAF has had no option but to develop a policy of corrosion prevention. Aerospace Maintenance, Development and Support, part of Headquarters Royal Air Force Logistics Command, has therefore been actively involved with the evaluation and trialling of a range of important corrosion prevention techniques that are compatible with the RAF’s current stance. Aircraft washing and rinsing practices have been reviewed to confirm their effectiveness, and trials have shown that dehumidified air permeates readily through a full‐size airframe, reducing relative humidity and arresting the rate of corrosion. From our work we have concluded that effective washing should be supported, where possible, by freshwater rinsing, and, if a cost effective system can be developed, structural dehumidification should also be practised. Notwithstanding a policy of corrosion prevention, we know that we operate aircraft that have already accumulated corrosion damage which has to be located and recorded. Non‐destructive testing is employed widely, and the use of information derived from the process to populate structural databases is being explored. Additionally, we are involved with refining the methodologies associated with structural inspections to ensure the ongoing integrity of our ageing aircraft fleets.

Summarizes the RAF's need to keep aircraft in service for longer. Provides details of present anti‐corrosion methods employed and explains the RAF's involvement in design and manufacture of the aircraft, as this is where problems begin. Discusses the various forms of training in corrosion provided to those in the RAF, before examining corrosion prevention. Finally, discusses various non‐destructive tests used.

Considers briefly the history of corrosion in metallic aircraft. Summarizes the different types of corrosion which affect aircraft and the methods for monitoring and measuring this corrosion. Presents an alternative approach called “controlled search peening” where the induced surface compressive stresses stretch and yield the outer material surface and induce visible blistering and flaking at the surface, indicating the existence of exfoliation corrosion.

The second day of the Aerospace Corrosion Control Symposium, held at the Rai, Amsterdam, commenced with a paper presented by Aydin Akdeniz of the Boeing Commercial Airplane Group, USA. Entitled “Integrated Structural Maintenance Programme”, it outlined surveys conducted by Boeing of selected ageing aircraft to review the condition of the structure along with the airlines' maintenance practices. The results suggest that there is a great variation in the actual levels or degree of structural corrosion in the aircraft fleets. The paper gave a background to corrosion prevention and control programmes (CPCPs) and outlined a procedure for consolidating the CPCP with other structural maintenance tasks. It concluded that properly scheduled structural inspection and correctly applied ageing aircraft programmes establish minimum standards to ensure continued airworthiness (see Figure 1).

IT is impossible to obtain accurate information on the cost of aircraft corrosion to the civil airline operators and the armed services. The true cost should include aircraft washing and cleaning, the cost of inspection, the application of supplementary protectives and maintenance of the protective scheme as well as the cost of blending out corrosion damage and the replacement of parts which cannot be repaired. The removal of paint and repainting are further items which must be included in the overall corrosion costs. Estimates made by IATA in 1982 suggested that member airlines were spending the order of 200 million dollars per year on corrosion rectification or the equivalent of 8 to 20 dollars per flying hour depending on the aircraft type or operator. More recently it has been suggested that the actual cost of corrosion to the USAF is probably about one billion dollars per year.

Held recently in Amsterdam, the 3rd Aerospace Corrosion Control Symposium attracted speakers and delegates from a wide spectrum of the Aerospace industry, as well as from universities and research bodies. Discussion, debate and the exchange of information were facilitated by the presence of over 50 nationalities.

An overview of the advances in understanding the impact of corrosion on structural integrity and the associated tools available for inspection, assessment and repair is presented. A comprehensive set of these tools would allow for a significant shift in aircraft maintenance concepts.

The prevention of corrosion in the structures, engines and ancillary equipment of aircraft presents the corrosion engineer with a unique problem of the severest magnitude. Failure to provide adequate protection under all conditions will produce catastrophic results or, assuming that the affected parts are discovered in time, a costly replacement scheme.

The current corrosion maintenance philosophy reflected in aviation regulations and recommended practices does not stimulate progress in corrosion related technology. A US Air Force (USAF)‐sponsored survey has recommended re‐examination of corrosion maintenance policies and practices to identify lower cost alternatives, and has encouraged research into tools and techniques that reduce maintenance costs while preserving safety. In particular, these include models to predict the impact of existing corrosion damage on structural integrity, methods of predicting corrosion growth rates and nondestructive inspection systems capable of providing corrosion metrics. The Institute for Aerospace Research of the National Research Council Canada (IAR/NRC) has pioneered work on the application of enhanced visual methods for corrosion detection in lap joints and the assessment of the impact of corrosion on lap‐joint structural integrity. The role of these enhanced visual methods in the new corrosion management is described.

HIGH efficiency is essential in aircraft structures and corrosion protection is critical. Whether the corrosion is readily apparent or of a kind that degrades the mechanical properties of a joint, for example, without much visible evidence, serious reductions in static or fatigue strength can result. Because of the widely different climatic conditions in which aircraft operate, the rate of corrosion varies considerably. It can only take place where water either as a liquid or water vapour in air of high humidity, is present. A metal will not corrode if it is completely dry.