The paper describes an assessment of thickness and quality of hot-dip galvanised coating by means of the glow discharge optical emission spectrometry method (GDOES). For comparison, a metallographic analysis was made using an optical microscope. An important factor influencing thickness and quality of the hot-dip galvanised coating is chemical composition of steel, particularly the amounts of silicon. Structural steels with a low amount of silicon S235JR and S355J2 were chosen for the experiment and high-strength steel S690QL with a high amount of silicon was chosen for comparative purposes. The results of the coating thickness measurement by means of GDOES and optical microscopy show only minimal differences. Steel S690QL shows a thick and uneven zinc coating. In the case of steels S235JR and S355J2 an optimal hot-dip galvanised coating was observed.

This paper deals with the evaluation of the surface of structural steel whose samples were deliberately contaminated with transparent spray primer, adhesive label glue, and welding sprays prior to hot-dip galvanizing. The galvanized samples were studied by optical microscopy, GDOES, adhesion tests, and condensation humidity tests. The effect of surface contamination on the quality of the zinc coating was found to be significant. In some cases, the zinc coating is damaged (after contamination with welding sprays), in others, it is completely absent (after contamination with spray primer or adhesive label glue).

The aim of this paper is to consider the possibility of using Glow Discharge Optical Emission Spectroscopy (GDOES) for determination of carburized layer thickness. Carburized layer increases the hardness of basic material (low carbon steels with carbon content of 0.2%), thereby it increases its wear and abrasion resistance and it decreases forming of oxidation layer too. The thickness of this layer is usually determined by hardness measuring according to the CSN EN ISO 2639 standard. The results of this standardized method are compared with the results obtained by two methods of GDOES and with pictures of optical microscopy. It has been found that the method of "Bulk" GDOES analysis with gradual grinding is suitable for determining the thickness of carbon enriched layers, while carburized layers which would correspond to standardized hardness 550 HV 1 may be only guessed from the graph of dependence of carbon content on the depth, in which analysis was performed. The pictures from the optical microscope in cross section do not have sufficient predictive value.