SIBAE (‘Sociedad Iberoamericana de Electroquímica’) invites to the 23rd edition of the biennial congress that convokes researchers and students from mainly Spanish and Portuguese speaking countries. This is the first time that a SIBAE congress will take place in Peru. Continue reading…
Immersed electrochemical module (IEM) is an electrochemical half-cell with one or two ion-exchange membranes and an inner electrode. IEM is immersed directly into a tank with a process solution in order to produce certain changes in its composition, for example, to recover nickel ions from spent electroless nickel plating solutions. Another area of application is to maintain the stable composition of process solutions such as various etchants used in the manufacture of PCBs, stripping and passivating solutions based on chromic acid and its salts. Stabilizing is achieved by anodic regeneration of an oxidant (chromate, ferric, cupric or persulfate ions) which are consumed in the course of the operation of the solution, by removing accumulating reaction products (various metal ions) and maintaining desirable pH value in the process solution. Continuous operation of such modules allows to eliminate periodic dumping and to reduce considerably consumption of chemicals used for replenishments. IEMs are used in many plating shops for continuous regeneration of chromate-based zinc passivating solutions. Another area of application of IMF is a continuous purification of water in reclaim tanks which allows to reduce the consumption of fresh water for rinsing and the amount of waste water. Metals such as zinc, copper, cadmium and tin are recovered from reclaim tanks equipped with IEMs and are usually returned into plating tanks. Nickel metal is utilized in some other way. Chromic acid which is recovered from reclaim tanks with IEMs contains no cationic impurities. It is returned into chromium plating or passivating process solutions. The operation of IEMs in reclaim tanks after chromium plating, anodizing or passivating in chromate-containing solutions allows to reduce the consumption of chemicals and the amount of waste. Installation of IEM does not need any additional floor space, pipe lines, etc. They are especially effective in chromating tanks and small-scale cadmium plating lines, where their use can solve problems related with the environment protection. IEMs are used in Russia in many captive plating shops.
In this paper the influence of a mid-phosphorous electroless nickel coating on EN-AW 2618A was studied. Special emphasis was put on the metalturn-over (MTO) and a heat treatment on the coating properties and their influence on the fatigue properties. The increasing MTO leads to an increase in phosphorous content resulting in a reduction of hardness, while the ductility is much less affected. The low temperature heat treatment increases the hardness through a crystal growth. The fatigue tests show, that the electroless nickel coating can both have a positive as well as a negative influence on the fatigue properties. At higher mechanical stresses the deposit tends to reduce the lifetime, while at lower loads the lifetime gets increased. The reduction of lifetime is caused by defects in the coating which act as stress concentrators. An increase in MTO leads to a higher amount of coating defects and therefore a higher possibility for a reduction of the lifetime. Further research has to focus on the growth mechanisms of those defects since their influence seems to be more significant than other factors like the phosphorous content.
The demand for Zinc Nickel coatings continuously increases in the automotive industry. Especially interesting are zinc nickel alloys with a nickel incorporation of 12–16 %, due to their high corrosion protection as well as superior wear and heat resistance as compared to pure zinc and other zinc alloy coatings.
Despite many advantages of acid Zn-Ni electrolytes there are still some areas of application, like barrel plating or plating of complex-shaped parts, believed to be reserved for alkaline processes. In this paper zinc nickel coatings deposited from ammonium and boric acid-free acid zinc nickel electrolytes, with improved throwing power for rack and barrel applications are investigated. Their corrosion resistance, ductility and hardness will be presented. Moreover, their texture and morphology will be investigated using SEM, XRD and FIB methods. In the end thickness distribution and Ni-incorporation will be presented and compared to alkaline systems.