Influence of Alloy Composition on Performance of Zinc-Nickel Coatings

Electrodeposited zinc-nickel coatings are broadly used as sacrificial coatings for steel since many years in the automotive industry and for other high corrosion resistant applications. The best corrosion resistance is obtained with ZnNi deposits having 12–15 % Ni in the alloy. Many studies were performed showing the influence of nickel content in the alloy [1]. In industrial plating electrolytes other metals than Zn and Ni can be present. In alkaline zinc-nickel electrolytes mild steel is usually used as anode material. Depending on electrolyte composition and plating conditions more or less iron can be dissolved by anodic dissolution into the electrolyte. It is well known that the iron is codeposited into the zinc nickel alloy, but the effect on the alloy properties was never systematically investigated. In this study the influence of up to 800 mg/L iron in commercially used alkaline zinc nickel processes is investigated. Up to 8 % iron is amorphously codeposited in the alloy. No new iron containing phases could be detected by X-ray diffraction (XRD). ZnNi g-phases (Ni2Zn11/Ni5Zn21) are still the dominant phases, but plain orientation can be affected by iron codeposition. Corrosion properties are investigated by electrochemical measurements and neutral salt spray test. Whereas no huge difference in the corrosion properties between the bare ZnNi and ZnNiFe coatings was observed, the corrosion resistance with a subsequent trivalent chromium passivate can be drastically improved using iron in the alloy. 


Post Treatment of Anodising Layers / Nickel- and Cobalt free Alternatives Working at Ambient Temperatures

NickFor post treating anodising layers on aluminium, typically two different technologies are applied, the hot water sealing at 96-100 °C and the cold sealing using reactive salts to plug the pores of the anodic coating. Both applications show major disadvantages. Whereas the hot water sealing is extremely energy consuming due to the mandatory hot process temperature, the low temperature sealing processes typically apply nickel compounds being harmful to the environment. Nickel salts are toxic and carcinogenetic, having irreversible effects on the human body and health. Furthermore, nickel containing waste waters are difficult to treat, especially when also aluminium is present [1]. New nickel-free technologies have been developed accordingly, enabling a low temperature application yielding in major energy savings. The deposition of antisoluble compounds in the pores of the anodizing layer leads to best stability and corrosion protection, exceeding the performance of hot water sealing. The new process solutions as being non-toxic are less risky to store and to handle, assisting the safety at work. Implementing a new photometrical method for analysing the ingredients, process stability and production quality can be improved [2]. In some cases, the pH-resistance of the anodised surface can be enhanced, extending the application field of anodised aluminium. Moreover, the waste water treatment of the rinses is carried out at pH 9–10, hence, can be done mutually with aluminium containing effluents. 


Hybridisation as an efficient joining, electrochemical corrosion study as a need

The composite technology allows the development of structures with a high degree of integration, where the number of elements and auxiliary means for their structural joining are minimised. This can only be achieved by the use of appropriate manufacturing and design processes. Some advantages of such an efficient integration would be the low installation and inspection efforts, shorter cycle times in the production, higher robustness and lower manufacturing costs. Despite this high potential, joining these highly integrated parts is indispensable because of restrictions concerning the components’ complexity, repair requirements as well as material specific limitations [1].


Electrochemical Deposition and Characterization of Conjugated Copolymers of Thiophene and Aniline

A new series of copolymers, obtained by reacting aniline as electron donor with thiophene as electron acceptor in a donor–acceptor structure (poly-thio-co-ani), were synthesized via electrochemical polymerization using acetonitrile as a solvent and lithium perchlorate as supporting electrolyte. The copolymer have better solubility in DMSO and KOH than the corresponding homopolymers. Copolymerization of aniline and thiophene was studied by UV-visible and FT-IR spectroscopy. In order to analyze their structure and characteristics X-ray diffraction analysis was applied and the samples were photographed under scanning electron microscope (SEM) for microstructure analysis and morphological property. Electrochemical properties were observed by cyclic voltammetry.


Adsorption and inhibitive properties of aqueous extracts of rosmarinus as a green corrosion extract for copper in HNO3

The efficiency of plant extract as corrosion extract for copper in 1M HNO3 medium was carried out using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. The results showed variation in inhibition performance of the extract with varying concentration, immersion time and temperature. Langmuir isotherm was tested to describe the adsorption behavior of the extract on the copper surface. Potentiodynamic polarization study clearly revealed that this extract acts as a mixed type inhibitor i.e. the addition of the extract enhances both cathodic and anodic reactions. The results of the electrochemical impedance study showed a decrease in double layer capacitance and an increase in the charge transfer resistance. The results showed that rosmarinus extract could play significant role as corrosion inhibitor for copper in 1M HMO3.