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The “Linde Test” - A Screening Method for Biodegradable Oils with Respect to Copper-Alloy-Corrosion
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Abstract
The compatibility of biodegradable fluids (1) with copper-based alloys was found to be an important requirement for high-pressure mobile hydraulic systems. Existing test methods (2)(3)(4), are not suitable for determining the practical requirements for biodegradable oils, nor do they encourage or contribute to further development of such fluids. Our laboratories developed a screening method capable of establishing correlation between field experience and the results of accelerated tests. Test parameters include copper-alloy materials, temperature, different mixtures of biodegradable oils with mineral oils and water, as well as the simulation of mechanical activation of the ‘corroding’ surfaces. It is suggested that the ‘Linde-test’ provides a simple, quick and low-cost laboratory method to determine the compatibility of biodegradable oils with copper-alloys in hydraulic systems under conditions representative of practical applications.
Round Robin tests performed by the German VDMA also resulted in good correlations. VDMA is currently in the process of recommending standards for biodegradable oils based among others on the work described in this paper.
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Citation
Krause, B., Megerlin, F., and Oswald, H., "The “Linde Test” - A Screening Method for Biodegradable Oils with Respect to Copper-Alloy-Corrosion," SAE Technical Paper 981516, 1998, https://doi.org/10.4271/981516.Also In
References
- ISO / DIS 6743-4 Lubricants, Industrial Oils and Related Products
- DIN 51554 Test of Susceptibility to Ageing According to Baader
- ASTM D 130 Copper Strip Test
- ASTM D 4310 Oxidation Stability (TOST)
- VDMA 24 568 Harmonisation Sheet, Fluid Power, Rapidly Biologically Degradable Hydraulic Fluids, Minimum Technical Requirements March 1994
- VDMA 24 569 Harmonisation Sheet, Fluid Power, Rapidly Biologically Degradable Hydraulic Fluids, Guidelines for the Conversion from Hydraulic Fluids Based on Mineral Oils of DIN 51524 Type to Rapidly Biologically Degradable Liquid Pressure Media and the Measures, which Have to be Taken when Working with them March 1994
- ISO 6618 Total Acid Number (TAN)
- ISO 3104 Viscosity