Tribological performance of thin organic permanent coatings deposited on 55%Al-Zn coated steel - influence of coating composition and thickness on friction and wear

Dry lubricants are today increasingly being used in various types of sheet metal forming operations. Among these, permanent coatings, based on organic resins are the only lubricants which have the potential to increase the formability without additional lubrication, serve as temporary corrosion protection during transportation and, finally, serve as a pre-treatment before subsequent painting. In the present study, the influence of coating composition and thickness on the friction and wear behaviour of different thin organic permanent coatings deposited on 55%Al-Zn coated steel sheet have been evaluated by various types of laboratory tests. Surface profilometry, scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used in order to characterise and model the tribological behaviour of the coatings. The results obtained show that the tribological properties of thin organic permanent coatings are strongly influenced by the coating thickness. In order to reduce problems associated with high friction and galling, the coating must be deposited with a uniform thickness, i.e. uncoated regions must be avoided. Furthermore, the addition of various types of additives can be used in order to further improve the tribological performance of these types of coatings. (C) 2001 Elsevier Science B.V. All rights reserved.