400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org 2005-01-1812 Corrosion Preventing Characteristics of Military Hydraulic Fluids Jill M. Tebbe, Luis A. Villahermosa and Ralph B. Mowery US ARMY RDECOM Reprinted From: Military Vehicle Technology (SP-1962) 2005 SAE World Congress Detroit, Michigan April 11-14, 2005 SAE TECHNICAL PAPER SERIESDownloaded from SAE International by University of Minnesota, Tuesday, July 31, 2018ISSN 0148-7191 Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is publ ished in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 3 00 word abstract to Secretary, Engineering Meetings Board, SAE. Printed in USA For multiple print copies contact: SAE Customer Service Tel: 877-606-7323 (in side USA and Canada) Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: [email protected] permission and licen sing requests contact: SAE Permissions 400 Commonwealth Drive Warrendale, PA 15096-0001-USAEmail: [email protected] : 724-772-4028 : 724-772-4891 Tel Fax Downloaded from SAE International by University of Minnesota, Tuesday, July 31, 20182005-01-1812 Corrosion Preventing Characteristics of Military Hydraulic Fluids Jill M. Tebbe, Luis A. Villahermosa and Ralph B. Mowery US ARMY RDECOM ABSTRACT Hydraulic systems are widely used in a variety of military applications such as aircraft, ground vehicles, and weapon systems. The impact of corrosion on hydraulic systems and its components has been identified but is often not recognized 1. Project collaboration between the U.S. Army Research Lab, U.S. Army Corrosion Office, and Concurrent Technologies Corporation identified the most critical corrosion issues found in hydraulic systems to be hoses, hose end fittings, actuator arms, pistons, cylinders, and rams. INTRODUCTION Corrosion, by definition, is the deterioration of a metallic surface by chemical or electrochemical action. Common causes of metal corrosion range from humid air entering a hydraulic system and its subsequent condensation, to the chemistry of the hydraulic fluid, to the interaction of metals with different electrochemical potentials. It is important to note that co rrosion and rusting are not interchangeable terms. Corrosion often results in a weight loss and surface pitting which exposes the metal. Thus, the exposed metal can react with water and air to form iron oxides (rust). There has been some discussion and disagreement among the various Military Service’s Subject Matter Experts (SME) about the need for corrosion inhibited hydraulic fluids. It has been shown that corrosion preservatives can cause sticking of critical servo and poppet valves in some aviati on systems. Therefore, hydraulic fluids containing corrosion preventatives have been prohibited in aviation hydr aulic systems by the US Air Force, US Naval Aviation and in US Army Aviation. However, given the relatively dirty operating environment of Army ground equipment, corrosion inhibited fluids are considered necessary. To prevent corrosion in hydrau lic systems, the Army has specified the use of hydraulic fluids with corrosion preventing and/or rust inhibi ting characteristics. The most common corrosion inhibitor currently used in hydraulic fluids is barium dinonyl napthalene sulfonate (BDNS). Corrosion inhibitors typically used in engine oils are unavailable because of inclusion in the proprietary additive package. Currently, the Army uses two different types of hydraulic fluid and in many instances; engine oil is used as a hydraulic fluid in Army vehicles. To verify the relative corrosion protection performa