Effect of coating parameters on microstructure, corrosion behavior, hardness and formability of hot-dip Galfan and galvanized coatings

In the current study, zinc–aluminum (Galfan) and zinc (galvanized) coatings were coated on steel sheets using the hot-dip technique. The effect of process parameters on the microstructure, corrosion behavior, hardness, and formability of the coatings was assessed. The results demonstrated that both the corrosion area and corrosion rate of the galvanized coatings were reduced by increasing the immersion time. In contrast, the process temperature did not affect the corrosion behavior. Furthermore, by prolonging the dipping time, the hardness of the coatings decreased. The Galfan coatings showed higher formability and the superiority of mechanical and corrosion properties of Galfan coatings over conventional galvanized coatings was indicated.

Pitting Corrosion of Hot-Dip Galvanized Coatings

Lead (Pb) addition to hot-dip galvanizing (HDG) baths affects the physical characteristics of zinc coatings and is also useful to protect kettles. The influence of lead additions on both corrosion rate and morphology as well as on structure of zinc coating is less investigated. In this paper, three different additions, (Pb = 0.4–0.8–1.2 w/w) were chosen for three series of steel substrates, plus references without lead. The three steels chosen as substrates contained silicon (Si) = 0.18, 0.028, 0.225 w/w, respectively. The experimental part included both macro- and micro-electrochemical measurements, weight loss vs. time plots, Glow Discharge Optical Emission Spectroscopy (GDOS) and SEM/EDX microanalysis of both surface and cross-section of samples. Lead concentration is responsible for evident bimetallic coupling in the surrounding of lead inclusion with consequent increased dissolution rate, chunk effect, and rougher surface morphology.

Change of Mechanical Properties of Zinc Coatings After Heat Treatment

Hot-dip galvanized coatings represent a protection based on passivation of the single zinc layer. It is one of the most commonly used surface treatments of steel. However, pure zinc forms merely an insignificant upper layer. Coating crosscut is formed by intermetallic phases that can cause decrease in the level of anticorrosion protection. This results from an iron diffusion from the base material. Goal of this paper is to analyse the changes in the mechanical properties of these phases in relation to zinc coating heat treatment. For the experiment, annealing temperatures of 200 °C and 300 °C were used, and the staying time was set at 1, 3 and 5 hours. Furthermore, samples without any heat treatment were subjected to comparison as well. Moreover, following tests were conducted: bending test in compliance with the ČSN EN ISO 1519 standard, and tearing test (in accordance with the ČSN EN ISO 4624 standard). On the basis of performed tests, the changes in mechanical properties of the zinc coating after heat treatment could be analysed.

Analysis of Galvanized Coatings Applied on General Purpose Wire

The paper deals with applying hot-dip galvanized coatings on general purpose wire. Galvanized wire properties were generalized and structured as a hierarchical tree of properties. A set of experiments was carried out to analyze potential operation modes of the line and the application of steel wire. The coating quality forecasting technique was developed to implement a production process, ensuring the required properties of galvanized wire.