Contribution presents results of study of tribological characteristics of Fe-Zn coated steel sheets. Experimental research was done using coatings with different alloying -under alloyed, optimal and slightly pre alloyed. The optimally alloyed coatings and the slightly prealloyed ones were annealed in order to reach different alloying level. Alloying level was evaluated by phase composition and % Fe in coating. Tribological properties such as surface microgeometry, abrasion, friction coefficient were analysed from the view of formability. Experimental results of strip drawn test were used for verification of strip-drawn test numerical simulation. Based on numerical simulation results, contact pressure on drawing die radius was observed.Keywords: Fe-Zn coatings, steel sheets, coating morphology, friction coefficient, numerical simulation IntroductionCurrent production in the automotive, consumer goods industry and also other industries must adapt to many; often mutually conflicting technical, economic and environmental requirements. On the one hand, customer demands for products performance, primarily for safety, reliability, corrosion resistance, driving dynamics, comfort and economy are growing; on the other hand, pressure to reduce emissions, higher productivity, eco-friendly production, reduction of maintenance costs and prices of products is increasing. The main innovative trends for increasing the performance of automobiles include reducing the weight of structural parts that contribute the most to the total weight of the car (body 26 %, 23 % undercarriage, motor 21 %, 22 % equipment, etc.). The effectiveness of this approach has been demonstrated by the results of the project ULSAB. For more than 80% of structural elements of the ULSAB body the builders have used high-strength steels with yield strength from 210 to 550 MPa, ultra-high strength steels with yield strength above 550 MPa, almost half of the weight of the body consists of laser-welded tailored blanks (tailored blanks) and sandwich materials [1,2]. In order to ensure the adequate lifetime of autobodies, majority of structural elements of ULSAB body are made of zinc coated sheets. Among the coated steel sheets are given the ratio between quality and the price of its irreplaceable galvanized sheets. During annealing after galvanization the transformation of the

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The performance of hot-dip coated steel sheets is associated with properties of the zinc coatings on steel substrate. For the characterization of the adhesion behaviour of zinc coating on steel various tests were employed. The study was focused on quantification assessment of galvanized coating adhesion to substrates. Methods for evaluation of the bonding strength of zinc coating by the shear strength and the T-peel tests applying four special types of adhesives were used. The experimental tests of bonded joints show that the adhesion of the zinc coating to the substrate was higher than that of the applied adhesive with the highest strength.

In the paper mutual comparison of zinc coatings enriched with small additions of Mg and Al (up to 1 wt.% Mg and 1 wt.% Al) and traditional zinc coatings produced by hot dip galvanizing, concerning some important properties of coatings like coating structure, cracks formation after deformation and corrosion resistance of deformed samples was studied. It was shown, that while traditional hot-dip zinc coatings are formed by homogenous zinc layer, exhibiting only low amount of soluble aluminium, coatings enriched by small amounts of Mg and Al, namely 0.6% Mg and 0.8% Al are formed by dendritic zinc matrix and interdendritic phase containing Zn-Mg-Al eutectics. Development of cracks was investigated in the area of maximal deformation of the samples subjected to stretching. It was found, that while traditional zinc coatings showed sporadic long fine cracks, zinc coatings enriched with Mg and Al exhibited aggregation of short thick cracks in the deformed area. Samples of both materials after stretching were also exposed in neutral salt spray atmosphere in corrosion chamber. It can be concluded, that material with coatings enriched with Mg and Al showed better results in corrosion tests contrary to the presence of massive cracks in the coating. This significantly increased corrosion resistance is possible due to excellent adhesion of zinc coatings, containing Mg and Al on drawing steels.

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