Corrosion failures of components in electro-hydraulic control systems can have serious
consequences for the operation of an entire subsea oil recovery system. The principal objective of
this study is to assess the corrosion behaviour of the main material of construction used for the
components in such systems (Stainless Steel 316L) in a range of commercial hydraulic fluids
(Oceanic HW443, HW525, HW540, HT, EE1), all of which are water-based and mainly contain
ethylene glycol as an antifreeze constituent [1] with some other additives such as sodium sulphonates,
fatty acid esters, esters of phosphoric acid, amine salts, carboxylic acids and acid esters up to 10%
[2]. These systems are located in deep seawater, and some failures have been suggested to be induced
by the ingress of seawater under high pressure. The paper tests this hypothesis.