Surface Technology最新文献

Corrosion inhibition by 3-(alditol-1-yl)-1,2,4-triazolo(3,4-a)phthalazine and some related compounds of aluminium in hydrochloric acid was measured using chemical and electrochemical methods. Polarization curves showed that these compounds are cathodic inhibitors. It was found that the efficiency of the inhibitor decreases with the increase in the number of the carbon atoms in the sugar moiety of the molecule. The effect of the substituent in the heterocyclic part on the inhibition efficiency was studied. The results are discussed on the basis of the structure-inhibition relationship and the interaction between the adsorbed layer of the inhibitor and the bulk solution.

The effects of undersaturation, temperature and stirring on the dissolution kinetics at dislocation sites in sodium chloride crystals in the etchant ethyl alcohol + cadmium chloride (as poison) have been studied. It is seen that the results are not consistent with the theoretical predictions.

The relation between MnO₂ structure models and electrochemical properties in the MnO₂-aqueous electrolyte interface is discussed.

It is shown that the formalism which takes into account structural water as neutral molecules and solvated protons gives the best interpretation of these properties.

This paper describes electrolytic stainproofing of copper foils in chromic acid solution containing suitable additives to produce a very thin protective film. The quality of stainproofing was checked by a tarnish resistance test, a solderability test and an etchability test. The treatment also offers good protection to copper and its alloys for very many applications in day to day life. The optimum bath composition consists of chromic acid 10 g 1^-1 and acetic acid 5 g l^-1 and operates at a cathodic current density of 2.5 A dm^-2 for 30 s at 30 °C.

Hitherto the classical formulae for calculation of the average stress in electrodeposits on the basis of the measured deflections of a strip bent as a result of one-sided plating have been widely used. A study of these formulae reveals that they do not show sufficient accuracy to satisfy all the equations of the mechanics. In view of this, a new theoretical model of the force interaction between the deposit and the substrate is proposed in this work and a new formula for calculating the average stress has been derived. The model conforms to the generally accepted simplifying assumptions made by other authors concerning the stress in electrodeposits, while at the same time accurately satisfying all the basic equations of the theory of thin elastic plates.

The electrochemical behaviour and corrosion of a commercial Egyptian 18-8 austenitic stainless steel was investigated in sulphuric acid and in sodium sulphate solutions using the potentiodynamic technique. In acid solution, the anodic polarization scans are characterized by the appearance of active, passive and transpassive transitions before oxygen evolution. The current densities corresponding to these three regions are increased by increasing either the acid concentration or the voltage scanning rate. The passive electrode does not regain its activity when subjected to cathodic treatment. Sensitization of the electrode enhances its susceptibility to intergranular corrosion.

In sodium sulphate solution, the polarization scans are characterized by the disappearance of the active region. On sensitization, a second transpassive region appears before oxygen evolution.

Differential capacitance measurements have been obtained over a range of electrode potentials to assess the effects of individual components of a commercially available mild steel corrosion inhibitor.

The purpose of this work is to use nuclear magnetic resonance (NMR) to characterize properties of HUO₂PO₄·4H₂O (HUP) pellets; these are currently used instead of powder in most applications involving solid electrolytes. The physical characteristics of HUP greatly depend on powder precipitation, washing and drying and pellet ageing conditions. NMR measurements were performed at various temperatures using two samples prepared with two different amounts of water. Identical results were obtained from both types of sample. These results are in agreement with those already reported and correspond to those of HUP powder. This result shows that NMR measurements characterize proton motion in HUP bulk rather than in the grain boundaries. An estimated value of D_H⁺ is found to be 10⁻⁷ cm² s⁻¹ at room temperature. This high value shows that HUP is a fast protonic conductor. Accordingly the proton diffusion in HUP is not expected to be the limiting step when this solid electrolyde is associated with a solid cathodically reduced by photon insertion.

Self-corrosion and the anodic behaviour of commercially pure aluminium (Al-2S) have been studied in sodium and potassium hydroxide solutions. The effects of calcium hydroxide and sodium or potassium citrate on the corrosion and anodic behaviour of 2S aluminium have been investigated. It is concluded from this preliminary study that 4 N NaOH and 4 N KOH containing Ca(OH)₂ and sodium or potassium citrate respectively in the correct proportions would serve as a suitable electrolyte for a possible aluminium alkaline primary battery.

Many relations exist for calculation of the spontaneous macrostress appearing in an electrodeposits plated on one side of a flexible strip cathode. In the present work a schematization of the deposit and the cathode is carried out and their state of stress examined by use of the finite element method. In this way the correctness of the theoretical models and of the more accurate formulae for calculation of macrostress in electrodeposits derived previously is proved. The determination of the force interaction between the deposit and the substrate was further refined, in comparison with that of Popereka.