Evaluation of the corrosion resistance of different galvanized steels treated in a cerium salt solution

Abstract

Analysis of polarization curves and impedance spectra has shown that the surface chemistry of galvanized steels plays an important role in determining their corrosion behavior. Zn-Ni samples that were untreated or had been treated in a 10 mM Ce(NO 3 ) 3 solution had the lowest corrosion rates in 0.5 N NaCl. The efficiency of the surface modification process was the highest for electrogalvanized steel. Surface analysis showed that the protective layers on Zn-Ni and electrogalvanized steel contained mainly cerium oxides/hydroxides, while the layer on hot-dipped steel consisted mainly of zinc hydroxide.

Testing and analysis techniques in rare earth inhibitor research

“…Typical results for experimental as well as fi tted data are shown in Fig. 2 85 Song and Mansfeld 87 further developed a new conversion coating process for EG steel based on a Ce(NO 3 ) 3 solution with some additives that reduced the total treatment time to 70 seconds, which would make this process more attractive for industrial applications. 87 The corrosion current densities of untreated and treated 2.12 Determination of I corr and Tafel slopes using the POLFIT program.…”

“…87 The corrosion current densities of untreated and treated 2.12 Determination of I corr and Tafel slopes using the POLFIT program. 85 EG samples were monitored during exposure to 0.5 N NaCl for 7 days using polarization and impedance data. The chemical composition of the coating layer was determined as a Ce-C-O-Si fi lm layer using SAM.…”

Evaluation of the Corrosion Resistance of Different Galvanized Steels Treated in Cerium Salt-Based Solutions

“…Aramaki modified the coating layer with Na 3 PO 4 to produce a self-healing effect that provided good corrosion protection especially in a scratched area [9]. Song and Mansfeld reported that the corrosion resistance and coating structure of cerium-based conversion films depended on the surface chemistry of different types of galvanized steel [10]. Colloidal silica and silane were employed as additives to enhance the corrosion protection of EG provided by a conversion coating that was formed in a molybdate-phosphate solution [11].…”

“…The amount of Ce 4+ was the highest in the film formed on EG. It was concluded that the protective layers formed on EG and EN contained mainly cerium oxide/hydroxide, while the layers on GA consisted mainly of zinc hydroxide [10,14].These results show that the substrate chemistry of galvanized steel plays a very important role in their corrosion resistance and in the efficiency of surface treatments used to improve their corrosion resistance [10,14]. …”

“…A factorial design approach was used to determine the optimum treatment conditions. The same approach was used for treatments in CeCl 3 + H 2 O 2 followed by treatment in Na 2 SiO 3 for sealing of the cerium oxide/hydroxide layer [12].The effect of the substrate chemistry of the galvanized steel samples on their corrosion resistance was evaluated by comparing the corrosion behavior of EG, EN and GI untreated or treated in 10 mM Ce(NO 3 ) 3 for 30 min during exposure to 0.5 N NaCl [10,14].Based on the results of these tests a final test procedure was developed in which the substrates were treated with two different processes that are denoted as Ce1 and Ce2. In process Ce1, the sample was dipped into 10mM Ce(NO 3 ) 3 for 30 minutes at room temperature, rinsed with purified water and dried by air blowing.…”