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Studies of inherent lubricity coatings for low surface roughness galvanised steel for automotive applications
Author(s) -
Hill Donald,
Holliman Peter J.,
McGettrick James,
Searle Justin,
Appelman Marco,
Chatterjee Pranesh,
Watson Trystan M.,
Worsley David
Publication year - 2017
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.1370
Subject(s) - lubricity , materials science , contact angle , diiodomethane , chemical engineering , lubricant , alkyl , surface roughness , wetting , composite material , surface finish , substrate (aquarium) , organic chemistry , chemistry , oceanography , engineering , geology
Abstract Surface lubricity on TiO 2 ‐coated galvanised steels can be controlled by solution depositing perfluorooctanoic ( C8 ), lauric ( C12 ) or stearic ( C18 ) acids to avoid lubricating oils/emulsions or substrate pre‐etching to remove surface oxide that add cost and waste. Water contact angles reveal increased surface hydrophobicity on coated samples that correlate with linear friction testing, suggesting water contact angle can be used to screen lubricity compounds. Linear friction testing shows that C12 and C18 lower the coefficient of friction ( μ ) by 50–60% compared with uncoated substrates whilst C8 drops μ from 0.31 to 0.22. Surfaces have been characterised by X‐ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy, whilst infrared confirms that as‐deposited coatings contain physisorbed and deprotonated acids chemisorbed through esters and thermal gravimetric analysis confirms increasing loadings from C8 to C12 to C18 . Surface washing removes physisorbed material and lowers μ by increasing surface organisation and alkyl chain packing that enhances frictional energy dissipation through steric quenching. Copyright © 2017 John Wiley & Sons, Ltd.