SECTOR FOCUS: MARINE


The rising tide of sustainable lubricants for marine applications


Martin Greaves, Research Leader, The Dow Chemical Company


Commercial shipping vessels make an estimated 1.7 million port visits each year, leaving up to 61 million litres of lubricant oils in their wake. Growing concern about the resulting impact on water quality has spurred global action in favour of replacing mineral oil-based lubricants with more environmentally benign alternatives.


In the U.S., for example, the Environmental Protection Agency (EPA) requires the use of Environmentally Acceptable Lubricants (EALs) in non-recreational vehicles over 79 feet operating in U.S. waters. To satisfy this requirement, lubricants must be biodegradable with a minimum of 60% degradation within 28 days, minimally toxic to aquatic life, and not bioaccumulative. Similar voluntary standards are in place in the European Union, China, Germany, Taiwan, Korea, Canada and a number of Nordic countries.


Of several base chemistries that meet EAL standards, synthetic esters have emerged as the leading alternative to mineral oils. Carefully designed synthetic esters are not subject to poor cold flow behavior or low thermo-oxidative stability, which are challenges when formulating with natural esters. Many synthetic esters


24 LUBE MAGAZINE NO.147 OCTOBER 2018


are readily biodegradable, low in toxicity, and can be tailor-made to impart lubricating properties specific to end-use applications. Despite growing interest in EALs, however, synthetic ester based lubricants account for less than five percent of the total marine lubricant market. This may be due, in part, to performance limitations resulting from poor hydrolytic stability, a characteristic common to many esters.


Both natural and synthetic esters are prone to hydrolysis, with potentially negative consequences any time an ester-based lubricant is exposed to a water-prone environment. This would apply to all below hull applications, and is an ongoing concern in deck applications. Exposure to water can accelerate acid formation in ester-based lubricants, resulting in hydrolytic breakdown and lubricant degradation. At best, more frequent lubricant replacement is necessary. At worst, machinery failure may result.


To improve the hydrolytic stability of ester-based lubricants, Dow recently introduced UCON™ WaterGuard Stabilizers, a line of biodegradable additives that extend the performance life of ester-based EALs. These additives are designed around Continued on page 26


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