Role of ethylamines on the electrochemical behavior of Fe-​Ni alloy films

Cyclic voltammetric expts. were carried out on platinum in acidic soln. (pH 3) contg. ferrous sulfate, nickel sulfate and ethylamines (EtNH2, Et2NH, Et3N)​. Spectral UV absorption studies indicate the complexation of both Fe2+ and Ni2+ ions with ethylamines. The results under transient polarization conditions indicate the redn. of Fe2+ ions through the intermediate species FeOH+, with second electron transfer as a slow step. The higher charge transfer rate of FeOH+ over NiOH+ redn. causes the anomalous codeposition of Fe-​Ni alloy film. Among the ethylamines, Et3N considerably assists the alloy deposition process. A gradual variation in free energy of alloy formation with Fe2+:Ni2+ (mol:mol) in the bath suggests the formation of an alloy intermediate phase rich in iron. Stripping voltammetric curves indicate the preferential dissoln. of iron from iron rich alloy intermediate phase. X-​ray diffraction studies further confirm the phase to be b.c.c. Fe-​Ni alloy. The extent of corrosion of the Fe-​Ni alloy film in the presence of ethylamines is in the following order: Et3N > Et2NH > EtNH2

Characterization of Zinc-Iron alloy electrodeposits for corrosion resistance

Zinc alloy plating is a high performance coatirrg. Compared to pure zinc plating, zinc alloys provide several advantages. A zinc alloy will generally provide superior sacrificial protection to steel. The degree of protection and rate of corrosion depends on the alloy metal and composition. The demand for higher-quali~~lo, nger-lasting, more corrosion-resistant coatings in industries such as aerospace. fkstener, electrical component and particularly, automotive has played a large role in the rlevelopment and use of zinc alloy coatings. Zinc-iron alloy has good weldabilily and ductility. In this paper the corrosion resistance properties of zinc-iron deposited from a sulphate bath are evaluated by electrochemical methods and the results are discussed

Electro catalytic amorphous nickel alloy

Nickel and nickel based alloy deposits are used as cathode materials for hydrogen evolution. Watt's bath modified with thiourea was used to deposit Ni-S and Ni-S-Co alloys. In presence of thiourea, Watt's bath offered amorphous Ni-S alloy. In presence of CoCI~ and thiourea, amorphous Ni-S-Co alloy was formed. Hydrogen evolution reaction occurred faster on amorphous Ni-S-Co alloy compared to amorphous Ni-S alloy from 28 wt% NaOH. Hydrogen evolution reaction rate increased with temperature on these amorphous alloys. A fast Volmer followed by slow Heyrovsky reaction occurred on the surfaces of these alloys. Heat treatment of amorphous Ni-S-Co alloy decreased the electro catalytic activity due to the disturbance in the amorphous structure

Role of furfuraldehyde on the electrodeposition of zinc

The kinetics of zinc electrodeposition on steel from alkaline tartrate bath was studied as a function of tartrate, sodium hydroxide and zinc ion concentrations. The rate of build up of the zinc deposition was found to obey the equation v = rate of build up = k (Zn2+{6 (OU-{S (tartrate)1.5. Additions of furfuraldehyde to the bath inhibited the rate of build up and the inhibition was due to adsorption of furfuraldehyde molecules on the growth sites of the zinc nucleus and controlled its growth. This inhibition decreased with current density. The hydrogen evolution reaction was favoured by furfuraldehyde

Correlation between structure and inhibition of organic compounds for acid corrosion of transition metals

In acid media, the corrosion inhibition offered by ethanol amines, benzoic acids, acetylinic alcohols for iron and nickel was investigated. These molecules absorbed on the metal surface and offered inhibition. A correlation between inhibition and electronic configuration of the molecules was attempted. In benzoic acids, the anchoring group is the benzene ring and the electron delocalization in the aromatic ring played a crucial role in the surface chelate formation. In the case of amines, the inhibition takes place due to absorption via lone pair of electrons on the nitrogen atoms. Acetylinic alcohols offered inhibition by accepting electrons from the vacant ‘d’ orbitals of the transition metals. On prolonged exposure in acid medium they form thick polymeric film on the metals thus offering inter-phase inhibitio

Some aspects of kinetics and mechanism of corrosion and passivation of metals in aqueous media

This thesis deals with the kinetics and mechanism of corrosion of zinc in concentrated sodium hydroxide solution and iron in phosphoric acid; the kinetics and mechanism of passivation of zinc in dilute NaoH solution and steel in sodium phosphate solutions. Corrosion and passivation of zinc: Kinetics and mechanism of corrosion of zinc in 1 N to 10 N Naoh solutions were studied by steady state and transient measurements. Both current step and potential step methods were used for transient measurements. The individual electrode reactions giving rise to the observed corrosion were studied in detail for transfer coefficients, reaction orders with respect to Na+ ion OH- ion, zinc(OH)4-2 ions and the rate determining steps identified. Using these equations relating icorr and Ecorr to solution parameters were derived and compared with the experimental dependence. The rate determining step for the anodic reaction obtained from the steady state measurements and this is explained in terms of mechanism of the anodic reaction. The kinetics and mechanism of passivation of zinc in dilute NaoH solutions was studied. The potential step method has been used to detect the number of minelayers formed on solid zinc before passivation. The analysis of the first peak shows two dimensional formation of passivation film with instantaneous nucleation. Dependence of the rate constant for the film growth on OH- ion concentration and potential shows that the rds is the discharge of OH- ions. Corrosion and passivation of iron and steel: Studies on the anodic and cathodic reactions involved in the corrosion of iron in H3PO4 which shows that the rate determining steps for the two reactions are similar to those reported for corrosion of iron in H2SO4. However the dependence of icorr and Ecorr on time and solution parameter shows that an additional factor in the corrosion of iron in H3PO4 Is the slow coverage of the surface with phosphate resulting in the decrease of corrosion rate with time. During the passivation of steel in NaH2PO4¬ solutions in the pH range of 3 to 5, three current peaks were observed. These are identified as peaks due to growth of phosphate film on the iron surface resulting in passivation of the metal. It is shown that in this case also film growth takes place in two dimensions with instantaneous nucleation. The dependence of the rate constant for film growth at pH, phosphate ion and ferrous ion concentration shows that the rds is Fe2+ surface Fe2+ lattice

Cyclic voltammetric studies on the electrochemical behaviour of cupronickel in sodium chloride solution

The electrochemical behavior of the dissolution of cupronickel in aqueous sodium chloride solutions was investigated through cyclic voltammetric and X-ray diffraction studies. The investigation analyses the discrepancies existing in the ideas related to cupronickel dissolution whether selective dissolution/simultaneous dissolution. Anodic dissolution of cupronickel alloys is found to be potential dependent. Selective dissolution takes place at lower potentials and simultaneous dissolution at higher potentials. The rate of simultaneous dissolution of the alloy is lower than that of the anodic dissolution of pure coppe

Porous iron electrode for alkaline batteries

A method for characterising the sintered iron electrode based on triangular potential sweep voltammetry has been developed. The peak potential separation and (Qc/Qa) at zero sweep rates have bean used as criteria of reversibili. The best composition based on using various iron powders, a - Fe304 and various additives has been recommended. Gasometric method to determine the self-discharge current and discharge studies of nickel-iron cell have been presente

Critical review on electrochemical quartz crystal micro balance - principles and applications to corrosion research

A