W. J. van Ooij

Study of Zn-Ni and Zn-Co alloy coatings electrodeposited on steel strips I: Alloy electrodeposition and adhesion of coatings to natural rubber compounds

Abstract The electrodeposition of Zn-Ni and Zn-Co binary alloy coatings on low carbon steel plates from simple acid baths has been studied. Coatings were examined for their composition, phase structure, morphology and deformability. Their properties and plating conditions were optimized such that these coatings would serve to formulate an improved composite coating systems for steel tire cords, replacing the conventional brass coating. In view of this, adhesion of several as-deposited and deformed coatings to a commercial natural rubber compound was evaluated. A dual-layer coating system consisting of a zinc-rich Zn-Co alloy underlayer and a nickel-rich Ni-Zn alloy top layer was found to exhibit characteristics most suitable for application on steel tire cords.

Study of Zn-Ni and Zn-Co alloy coatings electrodeposited on steel strips. II: Corrosion, dezincification and sulfidation of the alloy coatings

Abstract The results of electrochemical experiments and simple corrosion studies conducted on several Zn-Ni and Zn-Co alloy coatings with different phase structures and compositions are presented. Experimental studies exploring the dezincification and sulfidation behaviors of optimized dual-layer coatings consisting of a Zn-5wt.%Ni or Zn-1wt.%Co alloy underlayer and a thinner Ni-22wt.%Zn alloy surface layer, are also described. The results are discussed and compared with those of similar studies conducted with Cu-35wt.%Zn brass strips. Such qualitative comparisons illustrate the improved corrosion resistance and the retention of a high level of adhesion to natural rubber compounds of the new dual-layer coating system in a corrosive environment.

Paint delamination from electrocoated automotive steels during atmospheric corrosion. Part I. Hot-dip galvanized and electrogalvanized steel

—The mechanism of corrosion-induced paint delamination of electrocoated electrogalvanized and hot-dip galvanized automotive steels has been investigated. The materials were phosphated and electrocoated but not topcoated. The scribed panels were exposed to atmospheric conditions for 15 months. Two distinct regions were observed in cross-sectioned samples: a delamination zone without corrosion products which preceded a zone where the coating forms corrosion products, which consist largely of ZnO/Zn(OH)2. The mechanism of delamination is postulated to be mechanical in nature.

Characterization of high temperature hot dip galvanized coatings

Abstract High temperature hot dip galvanized (HT-HDG) coatings obtained on structural steels were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS) techniques. The coating was primarily composed of δ1 (Fe5Zn21, face-centered cubic (f.c.c.)) and ζ (FeZn13, monoclinic) phases. A comparison was made between galvannealed and HT-HDG coatings with regard to coating characteristics and properties, since both types of coating involve hot dip processes and contain Fe-Zn intermetallic phases.

A study of the mechanism of cathodic debonding of adhesively bonded neoprene rubber from steel

The feasibility of applying surface analysis techniques to study adhesion has been well established. Some of these techniques were utilized in this study of cathodic debonding of neoprene to steel bonds to examine the interfacial failure surfaces. Auger electron spectroscopy (AES) showed the poor cleaning capabilities of vapor degreasing and the modest effect of alkali on the oxide layer. The neat phenol-formaldehyde-based primer exhibited a significant amount of degradation characterized by changes in the chemical composition as shown by X-ray photoelectron spectroscopy (XPS). The analysis of the cathodically debonded surfaces showed cohesive failure in the primer close to the interface.

Chemical stability of phosphate conversion coatings on cold-rolled and electrogalvanized steels

Summary The attack of phosphate conversion coatings on cold-rolled (CRS) and electrogalvanized (EG) automotive steels in high and low pH solutions has been studied. Hopeite (HP) and phosphophyllite (PPH) crystals dissolve completely at pH below 3. HP also dissolves in alkali, whereas PPH is converted to a mixed oxide. The phosphate crystals have a pronounced texture which is influenced by the texture of the substrate. Certain orientations are more stable at high pH than others. There is a strong effect of the temperature on the chemical stability of the phosphate at high pH. The presence of NaCl increases the rate of phosphate attack at high pH. The mechanism of attack at high pH is a solid state reaction forming Zn(OH) 2 which is stabilized by iron, manganese and other ions resulting in the formation of complex zinc hydroxy compounds.

Corrosion of primed and fully painted precoated automotive steels in atmospheric and scab tests

The mechanism of cosmetic corrosion propagation and the types of corrosion products formed in painted precoated automotive steels during exposure to atmospheric and scab corrosion tests have been studied using SEM, EDX, XRD and static SIMS methods. The precoated steels were hot-dip galvanized (HDG), galvanneal (GA) and zinc-nickel electroplated steel (ZnNi). Exposure to atmospheric, marine conditions was for 15 months and in the Volvo scab test for 30 months. Corrosion was compared for electrocoated (EC) and for fully painted panels. In all systems studied and under both test conditions, underfilm corrosion propagated considerably further in the topcoated systems than in the panels that were EC-coated alone. In all EC-coated systems the corrosion product was identified as zinc hydroxychloride, whereas in all topcoated systems a mixture of zinc hydroxy-chloride and zinc hydroxychlorosulfate was found. Sulfur-containing pigments in the topcoat system were identified as the cause of the formation of the sulfur-containing corrosion product. A model is presented which accounts for the different corrosion rates of the EC-coated and topcoated systems.

Paint delamination from electrocoated automotive steels during atmospheric corrosion. Part II. Zinc alloy-coated steels

—In order to understand the mechanism of corrosion-induced paint delamination, the corrosion products formed in a series of electrocoated automotive precoated steels have been investigated. The materials were phosphated and electrocoated but not topcoated. The scribed panels were exposed to atmospheric conditions for 15 months. The steels were zinc-coated (electrogalvanized, hot-dip galvanized) and zinc alloy-coated (ZnNi, ZnFe, and ZnAl). In most systems two distinct regions were observed, namely a delamination zone without corrosion products which preceded a zone where the coating forms corrosion products. Most systems form ZnO/Zn(OH)2; ZnNi forms 4Zn(OH)2.ZnCl2. The mechanism of delamination is postulated to be mechanical in nature, i.e. by osmotic effects. Paint from ZnFe-coated steels does not delaminate. Suggestions for the further improvement of the corrosion resistance of painted automotive materials are given.

Characterization of Interfaces Between Polymers and Metals by Static Sims

The use of static Secondary Ion Mass Spectrometry (SIMS) in the characterization of polymer surfaces and interfaces between polymers and metals is described. Examples are given of the use of SIMS to study the effects of plasma treatments on polyimide surfaces and for the analysis of the interface in metallized polytetrafluoroethylene (PTFE).

A Static SIMS Study of Interfaces between Evaporated Metal Films and Polyimides

Static SIMS has been used to characterize the surfaces of a variety of commercial polyimides and of the interfaces between a polyimide of the PMDA-ODA type and evaporated films of copper and chromium. The commercial materials were all contaminated with organic and inorganic materials: the most common one is a free anhydride. The spectra obtained from the metal-PI interfaces are initially different for Cu and Cr but become identical after a post-deposition annealing treatment. A possible mechanism for the metal-polymer interaction based on the SIMS results is presented.