The behaviour and performance of materials used in the aviation industry is of paramount importance. Where lives depend on the correct selection and use of advanced materials on a daily basis and where even the smallest failure could have catastrophic consequences it is of paramount importance that the material is understood.

Two of the most important considerations are the effect that the elements may have on components, leading to corrosion; and the lubrication and wear of moving parts in the aircraft. Additionally, environmental concerns are leading to the development of alternative materials that must be of the highest possible specifications for use in such a safety-critical industry.

The papers in this briefing give important information on the corrosion behaviour of high specification materials used in the industry and also the performance of alternative lubricants.

Contents:

Corrosion inhibition of 6061-SiC by rare earth carbides

Metal matrix composites (MMC) are of great interest in the aerospace, military and automotive industries due to their good mechanical strength/density and stiffness/density ratios. A typical example might be the reinforcement of Al alloys with SiC particulates, which leads to a new generation of engineering materials. However, the addition of a reinforcing phase can cause discontinuities in any protective surface film, increasing the number of sites where corrosion can be initiated and rendering the composite liable to severe attack. This paper investigates if a suitable concentration of lanthanide salts (LaCl3 and CeCl3) could be identified that could improve both uniform and pitting corrosion resistance.

Originally published in Anti-Corrosion Methods and Materials Volume 54 Number 1, 2007

Corrosion of chromate conversion films on aluminium in electrically bonded interfaces

The effects of corrosion on materials degradation and component performance have long been recognized in the electronics and related industrial sectors such as aerospace. Recent studies have shown that corrosion is becoming a significant factor in the reliability of this equipment. One of the most severe problems that is unique to electronic systems is the failure of electrical contacts. This paper investigates the corrosion and electrical properties of the chromate conversion coatings on aluminium alloy Type 6061 in electrically bonded interfaces. A passive film layer containing chromate with alumina formed on the substrate and the good performance of this conversion coating was probably due to the characteristics of this protective film.

Originally published in Anti-Corrosion Methods and Materials Volume 54 Number 5, 2007

Copper redeposition and surface enrichment during the dissolution of Al-Cu alloys in different concentrations of NaCl solution. Part 1 – electrochemical measurements

Aluminum has weak mechanical properties and hence it is alloyed with other elements and then thermally treated to improve these properties. Aluminum alloys are widely used in different industrial applications such as electronic, aerospace, and automobile applications. This paper studies the dissolution of Aland Al-Cu alloys in different concentrations of NaCl using open circuit potential (OCP) and potentiostatic polarization measurements. The results reveal that cathodic current was controlled by the oxygen in solution, while the anodic current increased with increased Cu content in the alloy.

Originally published in Anti-Corrosion Methods and Materials Volume 54 Number 3, 2007

Electrochemical study of nanocrystalline plasma electrolytic carbonitriding of CP-Ti

Titanium and its alloys have a number of applications where weight reduction is of great concern. Nanocrystalline plasma electrolytic carbonitriding (PEC/N) treatments were applied on the surface of commercially pure titanium in a glycerol bath with different additives. All coated samples had a better electrochemical behaviour compared with the untreated substrate. The results obtained can be used wherever good corrosion and wear resistance with the highest efficiency is required. The speed of treatment by this technique makes this method very suitable for the industrial surface treatment of different components.

Originally published in Anti-Corrosion Methods and Materials Volume 54 Number 6, 2007

Esters of oxypropylated trimethylolpropanes as synthetic lubricants

Esters of straight-chain carboxylic acids with neopentylpolyols such as pentaerythritol, dipentaerythritol, and trimethylolpropane (TMP) are widely used as base fluids for Type 1 1/2 and Type 2 lubricants for aircraft gas turbine engines. An outstanding feature of this class of lubricants is the flexibility with which the physical properties can be altered by chemical modification. This paper provides detailed information on the experimental preparation of oxypropylated TMPs as synthetic base lubricants. The synthesized compounds show improved properties such as high viscosity at 100°C, low pour point, high flash point, and excellent viscosity-temperature properties compared to simple TMP esters and some literature reported ester-based lubricants.

Originally published in Industrial Lubrication and Tribology Volume 59 Number 1, 2007

Experimental investigation on system performance using palm oil as hydraulic fluid

Research in biodegradable and environmentally-friendly lubricants and hydraulic fluids has seen resurgence in recent years. The aim of this paper is to investigate hydraulic system performance using vegetable-based palm oil as hydraulic fluid. This vegetable-based palm oil could be a potentially-useful substitute for mineral-based energy transport media.

Originally published in Industrial Lubrication and Tribology Volume 59 Number 5, 2007