J. Mendala

The influence of Si addition in 55AlZn bath on the coating structures obtained in the batch hot-dip metallization

One of the methods of increasing the corrosion resistance of zinc coatings is the application of zinc and aluminium alloy baths in the metallization process. The coatings obtained are characterized by much better corrosion resistance thanks to the combination of aluminium properties, i.e. the barrier protection provided by naturally created aluminium oxides, with the capacity to protect the steel substrate, which is characteristic of zinc coatings. Zinc coatings with 55 wt. % Al and an addition of Si have gained industrial importance. The introduction of a third alloying component into the metallization bath is a technological addition, the aim of which is to reduce and possibly inhibit the aluminium diffusion towards the substrate. The article presents the results of the examination of coatings obtained in a 55AlZn bath at varied parameters of the technological process, as well as the specification of silicon addition influence on the structure and chemical composition of the coatings, and on the kinetics of growth. The coatings were obtained in three temperatures: 620, 640 and 660°C, and the process was conducted in a 55 wt. % Al bath with Si content of 0, 0.8 and 1.6 wt. % respectively, the remaining content was Zn. For the purposes of evaluating the microstructure and thickness of the coatings obtained, examinations on a light microscope were conducted. In order to determine the chemical composition of the coatings obtained, an EDS analysis was conducted. Quantitative examination of the chemical composition was carried out on the selected cross-sections of samples with coatings considered to be representative ones, using a SEM with a microanalysis system. Moreover, the linear distribution of elements on the cross-sections of the chosen coatings was determined. It is possible to state that the addition of silicon to 55AlZn baths allows reducing the uncontrolled growth of a layer. The layers obtained are more uniform, continuous and they show good adhesion to the substrate.

Corrosion Resistance of Zinc Coatings Obtained in High-Temperature Baths

We present the results of investigation of the technology of application of coatings in zinc baths at temperatures different from the standard temperatures of the process of galvanization. The corrosion resistance of the coatings is determined under the action of neutral salt mist and sulfur dioxide in the case of condensation of moisture. With the help of galvanization at elevated temperatures of 540–560°C, it is possible to obtain coatings of constant thickness with improved structure and higher corrosion resistance as compared with the coatings obtained at standard temperatures.

Investigation of the Initial Stage of Hot Dip Zinc Coatings on Iron Alloys with Various Silicon Contents

In this work tests on the course of zinc coating formation on model iron alloys with diversified silicon additions in molten zinc, with short times of contact at the solid-liquid border have been presented. The experiments were carried out at the temperature of 440°C. The assumed time of contact between solid and liquid phases was: 1, 4, 9, 14, 29, 59 seconds. The test stand was designed. The structure and thickness of coatings obtained on steel without silicon, on Sandelin steel and on high-silicon steel was defined. Based on the results we may ascertain that in the first stadium of the galvanizing process the impact of silicon upon the intensity of coating growth is small. Increased reactivity of silicon is already observed after about 29-59 seconds of the process.

Influence of the cooling method on the structure of 55AlZn coatings

In metallization processes, metals or metal alloys are used which have a low melting point and good anticorrosion properties. Moreover, they must form durable intermetallic compounds with iron or its alloys. The most common hot-dip metallization technology involves galvanizing, however, molten multi-component metal alloys are used as well. An addition of aluminium to the zinc bath causes an increase in corrosion resistance of the obtained coatings. The article presents results of tests of obtaining coatings by the batch hot-dip method in an 55AlZn bath. Kinetics of the coating growth in the tested alloys were determined in the changeable conditions of bath temperature, dip time and type of cooling. The structure of coatings and their phase composition were revealed. As a result of the tests performed, it has been found that an increase in total thickness of the coatings as a function of the dipping time at a constant temperature is almost of a parabolic nature, whereas an increase in the transient layer is of a linear nature. The structure was identified by the XRD analysis and the morphology of the coatings was tested by means of SEM. It has been found that the cooling process with the use of higher rates of cooling causes a size reduction of the structure in the outer layer and a reduction of thickness of both the intermediate diffusion layer and the whole coating by ca. 25 %.

The Influence of Substrate Roughness on the Surface Condition of WC-Co Coatings Obtained Using the Supersonic Method

Thermal spraying process is one of the main methods of obtaining the protective coatings. Coating quality largely depends on the proper selection of coating materials, technology and spraying equipment and the method of substrate preparation. The article presents the problem of the effect of surface preparation process on selected properties of the coating produced by supersonic thermal spraying – HVOF. Blast cleaning and supersonic thermal spraying processes were characterized. The influence of blasting parameters on the resulting surface profile and selected properties of the coating, such as roughness, porosity and structure were determined by means of surface profilometry, light microscopy and digital image analysis.

Corrosion Resistance of ZnAlMg Alloys for Batch Hot Dip Galvanizing

In the paper the results of corrosion resistance tests on ZnAlMg alloys used as batch hot dip galvanizing baths are presented. The tests were carried out on ZnAl alloys with 7 wt.% Al with the addition of 3 wt.% and 6 wt.% Mg. Corrosion resistance of tested alloys was compared with corrosion resistance of the traditional zinc bath alloy. Corrosion resistance of the alloys was defined by comparative methods in two standard corrosion tests in neutral salt spray and in moist atmosphere containing SO2. Electrochemical parameters of the corrosion process were determined on the basis of potentiodynamic tests. It was determined that the alloy of ZnAl7 has better corrosion resistance than the corrosion resistance of the alloy of a traditional zinc bath and that the addition of Mg to the alloy increases the corrosion resistance.

Mechanical Properties of Parts with Tin Coating Obtained by Hot-Dip Method

Hot-dip process leading to creation of protective coating is one of the effective ways to protect metals from corrosion. It provides the way to obtain the coating with required physical, mechanical and chemical properties. However, contact of solid metal part with the liquid metal bath during this process may lead to changes in mechanical properties or, in extreme cases, to premature failure of the part. This is mainly due to the effect called LME. The author has researched the likelihood of occurrence of this phenomenon in parts subjected to metallization in zinc bath or in zinc bath with additions of tin or bismuth. The presented results are a continuation of these research and include an assessment of the possibility of LME occurrence in parts metallized in tin bath and subjected to external stress.

Profilometric Assessment of Surface Condition of Zinc Coatings Formed by the Continuous Galvanizing Method

The paper presents the results of research on surface condition of zinc coatings. Profilometric studies were performed for zinc coatings formed in industrial continuous hot-dip galvanization process and for the same coatings after two years of use. The results include the geometrical shape of 2D and 3D surfaces, distribution of vertices on the surface and roughness and waviness profiles. The parameters Ra, Rz, Sa and Sz were used to define the surface roughness. The study was conducted using FRT Microprof optical profilometer with data acquisition and analysis by MARK III software package.

Zinc-Aluminum Coatings Obtained by Hot Dip Method on High Strength Steel for Link Chains

In the paper the author present the results of tests on obtaining zinc-aluminum coatings on the 23MnNiCrMo52 steel used for produce coil chains for the mining industry. The coatings was obtained in the eutectic zinc aluminum bath. The growth kinetics of the coatings has been defined, their structure has been developed and the chemical composition of particular structural components of the coating has been established. It has been determined that the obtained coatings are continuous and uniform and their morphology not depends on the chemical composition of the steel.

The Possibility of the LME Phenomenon in Elements Subjected to Metallization in Zn Bath with Bi Addition

Article presents the state of knowledge relating occurrences of liquid metals embrittlement. The results of experimental investigations of the LME phenomenon, reasons of its formation and influence of different parameters are described. In order to determine the basic mechanical properties of materials intended for research static tensile test was performed. Samples made of C66D and C70D steels with tensions stretching (500-800 MPa) at different values and kinds of loading during the hot dip metallization were investigated. Coating processes were made in zinc with 0.5% Bi addition and results were compared to zinc coating. The processes of hot dip metallization were done at 450°C temperature and immersion time 180 s. Coated samples were investigated by light microscope to specify possibility appear of LME effect.