Abstract
A new phosphate-free pretreatment from Henkel Corp. named TecTalis, was
investigated. The treatment bath is composed of dilute hexafluorozirconic acid with small
quantities of non-hazardous components containing Si and Cu. The performance of
treated steel was compared to samples treated in a phosphate conversion coating bath, in
simple hexafluorozirconic acid and in TecTalis without the addition of the Cu containing
component. Atomic Force Microscopy (AFM) and Transmission Electron Microscopy
(TEM) were used to characterize the coating surface morphology, structure and
composition. A Quartz Crystal Microbalance (QCM) was used for studying film growth
kinetics on thin films of pure Fe, Al and Zn. Electrochemical Impedance Spectroscopy
(EIS) was performed on treated and painted steel for studying long-term corrosion
performance of the coatings. The phosphate-free coating provided long-term corrosion
performance comparable to that of phosphate conversion coatings. The coatings
uniformly cover the surface in the form of 10-20 nm sized nodules and clusters of these
features up to 500 nm in size. The coatings are usually about 20-30 nm thick and are
mostly composed of Zr and O with enrichment of copper at randomly distributed
locations and clusters.
