Materials Performance Supplements


Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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Vapor Phase Inhibitors in Functional Fluids Boris A. Miksic, FNAcE, AllA FurMAN, roBErt kEAN, MArgAritA khArshAN, ANd liz AustiN, Cortec Corp., St. Paul, Minnesota The addition of corrosion inhibitors to lubricating compounds prolongs the service life of machinery during its working application and in storage. Cri- teria for selecting corrosion inhibitors for the equipment during transporta- tion, storage, and mothballing are based on their level of corrosion pro- tection for all metal elements while be- ing compatible with polymers (e.g., hoses and seals) and installed lubri- cants. According to the application re- quirements, the tests for such products include evaluation of their performance in environmental chambers, including humidity and salt fog, evaluation of va- por corrosion inhibition, immersion, and other corrosion tests. In operating equipment, corrosion inhibitors added to lubricating fuids should not nega- tively affect their lubricity, oil-water sep- aration, and other properties import- ant for such fuids. In addition to corrosion tests, evaluation of the fuid with added corrosion inhibitor includes testing of the essential properties listed in the fuid specifcations. This article presents the formulating approaches and evaluation of the performance of corrosion-inhibiting additives in func- tional fuids. The testing program is based on widely adopted standards. In a widely cited cost of corrosion study1 the direct cost of corrosion in the United States was estimated to equal $276 billion in 1998, approximately 3.1% of the coun- try's Gross Domestic Product. The indirect cost of corrosion is esti- mated to be at least equal to the direct cost. Examination of the data in 2013 indicates that total corrosion costs in the United States exceed $1 trillion annually. Internal surfaces of equipment corrode during all segments of their life: operation, intermediate operation, and storage. The reasons and the intensity of corrosion vary. Usually functional liquids don't cause cor- rosion. Corrosion occurs because of the contaminants in functional liquids, such as the presence of moisture, salts, acidity, and other corrosive species. In the majority of cases, corrosion can be prevented, delayed, or reduced by using corrosion inhibitors. The requirements of corrosion inhib- itors for functional f luids are different for equipment lay-up vs. equipment in use. Corrosion protection of machinery during mothballing can be achieved by using spe- cial rust preventatives or adding corrosion inhibitors to working lubricating oils. For such application the most important prop- erties of the rust preventative are the level of corrosion prevention; compatibility with all metals, plastics, and polymers used in the system; and sometimes removability. In operation mode, the corrosion inhib- itor additionally should not n egatively af fect the specified properties of lubri- cants. This requirement can be satisfied by using special formulas, limiting the dose rate, or using the inhibitor in combination with the additives, which can compensate for the negative effects of the rust preven- tative. Examples of successful applications of corrosion inhibitors in engine oils and fuels are described in publications. 2-3 The advantage of such products is that they can be high-performance lubricants, while at the same time possessing the ability to prevent corrosion in both storage and operation. This eliminates the necessity of changing the lubricant if equipment needs to be laid-up, returned back to operation, or used intermittently. Thi s ar ticl e pre sent s th e exampl e s of incorporating corrosion inhibitors in hydraulic f luids, both glycol/water-based and oil-based. Experimental Procedures Corrosion Inhibitor for Glycol/ Water-Based Hydraulic Fluid Two vapor corrosion inhibiting addi- tives (VCI-1 and VCI-1L) to glycol/water- based hydraulic fluid were formulated and evaluated. The main ingredients of these additives are a blend of amine salts of sat- urated iso-carboxylic and aromatic acids. Among e valuat ed extrem e pressure (EP) additives were several types of phos- phate esters and polyalkylene glycol-based products. VCI-1L consisted of 96% VCI-1 and 4% of a compatible high-performance EP lubricant. Two suitable EP lubricants were found in screening tests. Either can be used in formula VCI-1L when EP perfor- mance is required as a part of the package. When VCI-1L is made with EP additive 1, it is identified as VCI-1L1; when made with EP additive 2, it is identified as VCI-1L2. Results and descriptions identified only as VCI-1L apply to both formulations. Table 1 shows results of the additive analysis conducted by an independent lab- orator y using scanning electron micros- copy (SEM)-energ y dispersive spectros- copy (EDS). Table 2 shows the properties of VCI-1 and VCI-1L. These products are intended to be used in subsea equipment. Besides high performance in corrosion inhibition and lubricity, their impact on the sea environment had to be evaluated. VAPOR PHASE CORROSION INHIBITORS 4 JUNE 2016 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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