Kynal was a brand name for a series of aluminium alloys developed and originally produced by the British chemical manufacturer Imperial Chemical Industries (ICI).^[1] The name was derived from Kynoch, an existing ICI trademark for ammunition, and aluminium. It was largely used as substitute for Alclad, a popular corrosion-resistant aluminium alloy.

ICI produced Kynal in quantity at a facility in Waunarlwydd, outside Swansea. The material was extensively used by the British aviation industry during the Second World War, being recognised as a strategic resource. Numerous variations upon the material were devised by ICI around this time. During the 1950s, British Railways became a key consumer of Kynal, using the material on numerous members of its new fleet of diesel traction, including the first generation diesel multiple units (DMUs). By the twenty-first century, the material was largely considered to be obsolete, while the Waunarlwydd chemical works was permanently closed during the 2000s.

A key facility involved in the production of Kynal was the Ministry of Aircraft Production's factory at Waunarlwydd,^[2] near Swansea. ICI built and operated the plant on the government's behalf.^[3] Functionally, Kynal was similar to, and could be a substitute for, Alclad.^[4] Applications included various forged items, including pipework, vessels, and heat exchangers, as well as fuselage elements of aircraft.^[5][6] By 1938, the material was being producing at a very high volume as a consequence of the European powers having entered a period of rearmament around the time of Munich crisis, which led into the Second World War.^[7]

During the postwar era, Kynal continued to hold its strategic importance.^[8] The material proliferated throughout British engineering throughout the 1950s and 1960s; it began to be used in the frames of road vehicles during the mid 1950s.^[9] Kynal was used extensively for British Railways' modernisation of the 1950s, specifically in the construction of the publicly-owned organisation's new diesel fleet.^[10] The majority of the 'lightweight' diesel multiple units (DMUs) featured the material.^[11] Around the same era, the company was also involved in studies into the use of Kynal as a roofing material.^[12]

By the twenty-first century, Kynal was largely considered to be obsolete as a material.^[13] During the 2000s, the original Waunarlwydd plant, which was by then owned by Alcoa, was closed down.^[14][15] Despite this, research efforts into fields such as battery technology have involved the use of Kynal.^[16]

• Kycube, a similarly named series of copper beryllium alloys produced by IMI.