Magdalena Popczyk

Production and properties of composite layers based on an Ni–P amorphous matrix

Composite layers Ni–P + Co, Ni–P + W and Ni–P + Ti were obtained in galvanostatic conditions, at jdep = 0.200 A cm−2. The x-ray diffraction method was used to determine the phase composition of the layers and atomic absorption spectrometry was applied to specify their chemical composition. A metallographic microscope, stereoscopic microscope and Form Talysurf-type profilograph were used for cross-section and surface morphology characterization of the layers. The behaviour of the obtained layers was investigated in the process of hydrogen evolution reaction from 5 M KOH using classical methods (voltammetry, steady-state polarization) and electrochemical impedance spectroscopy (EIS). Based on recorded steady-state polarization curves, the Tafel equation parameters for this process were determined. EIS was used to study the interfacial properties at electrode overpotential ΔE = −0.200 V. It was found that the investigated Ni–P + Co layer is characterized by increased electrochemical activity for hydrogen evolution compared to Ni–P + W and Ni–P + Ti layers. Greater activity of the Ni–P + Co layer in this process may be attributed to the developed electrode surface. The values of surface roughness factor Rf were also determined.

The electrodeposition and properties of Zn-Ni + Ni composite coatings

The Zn-Ni+Ni coatings were deposited under galvanostatic conditions at the current density range from 20 to 60 mA cm−2. The influence of deposition current density on surface morphology, chemical and phase composition and corrosion resistance of obtained coatings, was investigated. Structural investigations were conducted by X-ray diffraction method. Surface morphology and surface chemical composition of the obtained coatings were determined by a scanning electron microscope. Studies of electrochemical corrosion resistance were carried out in the 5% NaCl solution, using potentiodynamic and Scanning Kelvin Probe (SKP) methods. A possibility of incorporation of nickel powder from a suspension bath to the Zn-Ni matrix, during galvanostatic deposition was demonstrated. The results of chemical composition analysis show that the Zn-Ni + Ni coatings contain approximately 15–18% at Ni. It was found that surface morphology, surface chemical and phase composition of Zn-Ni + Ni coatings depend in small degree on deposition current density. However, the current density influences distribution of nickel powder on the surface of these coatings. The optimal values of current density on account of corrosion resistance, are found to be j = 40–50 mA cm−2.

The Hydrogen Evolution Reaction on Electrolytic Nickel-Based Coatings Containing Metallic Molybdenum

Ni-Mo and Ni+Mo coatings were prepared by electrodeposition under the galvanostatic conditions, in such a manner that the coatings contain the same quantity of molybdenum. The electrochemical activity of these coatings was studied in the process of hydrogen evolution reaction (HER) from 5 M KOH solution using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. Basing on the results of EIS measurements, the rate constants of the HER as well as the surface roughness factors were determined. It was found that Ni+Mo composite coating is characterized by enhanced electrochemical activity towards hydrogen evolution as compared with Ni-Mo alloy coating. Improvement of the electrocatalytic performance of Ni+Mo composite coating could be attributed to the increase in its real surface area as well as to the catalytic effect in points of contact of molybdenum and nickel matrix. Thus obtained composite coating may be useful in application as electrode materials for the hydrogen evolution reaction.

Localized Electrochemical Impedance Spectroscopy for Studying the Corrosion Processes in a Nanoscale

This work deals with localized electrochemical impedance spectroscopy (LEIS) which is an improved technique of the commonly used electrochemical impedance spectroscopy (EIS). Thanks to modern structural solutions, the LEIS technique ensures local impedance measurement. Therefore, it is used in the research into point corrosion, such as the pitting corrosion, and in the research into protective coatings or into alloys including alloy steels. This review paper presents the basic theory and the usability of the LEIS based on the literature on the newest research in the field of corrosion.

Electrochemical Characterization of Nickel-Phosphorus Based Coatings Containing Cobalt

The Ni-P, Ni-Co-P and Ni-P+Co coatings were obtained in galvanostatic conditions at the current density of jdep= -200 mA cm-2. A stereoscopic microscope was used for surface morphology characterization of the coatings. The X-ray diffraction (XRD) method was used to determine phase composition of the coatings and the atomic absorption spectrometry (AAS) was applied to specify their chemical composition. The behavior of the obtained coatings was investigated in the process of hydrogen evolution reaction (HER) from 5 M KOH using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. It was found that introduction into Ni-P amorphous matrix powder of cobalt produced porous electrode materials which could be used for the HER.

The Influence of Current Density of Electrodeposition on the Electrochemical Properties of Ni-Mo Alloy Coatings

The Ni-Mo alloy coatings with a high content of Mo up to 44.5 at.%, were prepared by galvanostatic electrodeposition in the range of deposition current density, jdep, from-30 to-240 mA cm-2 from the nickel plating bath containing potassium pyrophosphate, nickel chloride, sodium molybdate, and sodium bicarbonate. Investigations of hydrogen evolution reaction (HER) were carried out in 5 M KOH solution at room temperature using steady-state polarization and electrochemical impedancy spectroscopy (EIS) measurements. It was found that for the Ni-Mo alloy coatings, the increase in their catalytic properties towards the HER with the increase in the value of jdep of the coatings, was due to the intrinsic activity.

Influence of thermal treatment on the corrosion resistance of electrolytic Zn–Ni+Ni composite coatings

This study was undertaken in order to obtain and characterize the corrosion resistance of Zn–Ni+Ni composite coatings. The influence of thermal treatment on surface morphology, phase composition, and corrosion resistance of Zn–Ni+Ni coating was investigated. The Zn–Ni+Ni coating was deposited under galvanostatic conditions (j = 40 mA cm−2). Thermal treatment was carried out in argon atmosphere. The surface morphology of Zn–Ni+Ni coatings was carried using a scanning electron microscope (JEOL JSM-6480) and the surface chemical composition was determined by the EDS method. Structural investigations were conducted by X-ray diffraction method. The studies of electrochemical corrosion resistance were carried out in a 5% NaCl solution, using potentiodynamic and scanning vibrating electrode (SVET) methods. On the grounds of corrosion investigations, it was stated that thermal treatment improves both total and localized corrosion resistance of Zn–Ni+Ni coating in a 5% NaCl water solution. The higher corrosion resistance of the thermally treated Zn–Ni+Ni coating could be attributed to the increase in the amount of zinc bonded to nickel in the form of Ni2Zn11 and Ni5Zn21 intermetallic phases. The SVET analysis indicated that thermal treatment of Zn–Ni+Ni coating causes a decrease in the number of corrosion centers on their surface area.

Application of the Scanning Kelvin Probe Technique for Characterization of Corrosion Interfaces

This paper deals with the basic theory and the usability of the scanning Kelvin probe (SKP) being a non-destructive, non-contact method for testing the condition of the surface of conductor, semiconductor and dielectric samples. This technique is based on the electron work function (EWF) characteristic of various test substances and depends, inter alia, on the sample surface condition. During measurement, the so-called surface potential distribution map containing information about EWF value is registered. Key applications of SKP and its various modifications to characterization of corrosion interfaces, have been presented based on the newest literature data covering the past two years of the active research in the field of corrosion in a nanoscale.

On the Use of the Scanning Electrochemical Microscopy in Corrosion Research

This paper deals with the basic theory and the usability of Scanning Electrochemical Microscopy (SECM) in corrosion research. The SECM is the in situ method of surface characterization which is based on the scanning of the tested surface using ultramicroelectrode and simultaneous electrochemical testing of the surface. This technique provides an electrochemical imaging of the surface. Key applications of SECM have been demonstrated based on the newest literature data covering the past two years of the active research in the field of corrosion in a nanoscale.

DC Current Electrodeposition of High Mo Content Ni-Mo Alloy Coatings from Alkaline Solutions

The binary Ni-Mo alloy coatings of high Mo content were obtained on a steel substrate by dc current electrodeposition from alkaline solutions of pH 7.5-9.0. The pyrophosphate baths contained nickel chloride as a source of nickel ions, and dihydrate sodium molybdate supplied molybdenum. The constant current electrodpeposition at the deposition current denisty of jd = 30-240 mA cm-2 was performed at 60°C. The physical and chemical properties of the obtained electrocoatings were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray fluorescence (XRF) methods. All obtained Ni-Mo alloys reveal the amorphous structure, and their chemical composition strongly depends on the operating parameters of electrodeposition. The maximal content of Mo was found to be 45 at.%. The complicated mechanism of the induced co-deposition of the Ni-Mo alloy, has been discussed.