Single Electrode Potential Research Articles

Electroless Cobalt Deposition from Acid Baths

An acid electroless cobalt plating bath was developed which utilizes di‐methylamine borane (DMAB) as the reducing agent and which provides bright deposits at over 13 μm/hr at 70°C. The bath, slightly modified, is also usable at room temperature for deposition on palladium‐activated nonconductors. Additions of even small quantities of hypophosphite to the DMAB bath resulted in failure to achieve deposition; the effect of hypophosphite additions on the single electrode potentials was determined and the results discussed. Electroless cobalt‐boron deposits were found superior, in some respects, to electroless nickel‐phosphorus for providing protection for steel against corrosive attack. A double layer deposit of electroless nickel plus electroless cobalt topcoat provided more effective protection for steel than either deposit, alone, of the same total thickness. Chromating treatments were found effective for retarding the tendency for tarnishing of cobalt during salt exposure. The magnetic properties of some electroless cobalt‐boron deposits were determined; the coercivity was considerably lower than that of electroless cobalt‐phosphorus deposits.

金蒸着薄膜の表面特性

Gravimetric and electrochemical studies were made on surface phenomena of evaporated gold by measuring the change in wieght, single electrode potential, and electric resistance of the thin films deposited under 1-3×10-5 Torr. The films showed some reactivity with oxygen in the dry air, though bulky gold is chemically inactive. The temperature of the film substrate had effects on the weight increase of the films due to oxidation and adsorption. The rate of weight increase of a film prepared at 30°C was lower than that of a film prepared at 200°C, but the total amount of oxygen adsorbed on the former film was greater than that adsorbed on the latter film. A very thin film obtained on the substrate of 30°C by low rate of evaporation showed a peculiar process of weight change with time in the dry air; the process was quite different from those of ther films. That is, the weight increase of the film due to adsorption of oxygen continued for about 1hr., and then, gradually decreased. It was found by the measurement of single electrode potential that the deposit prepared by high deposition rate on the substrate at a low temperature (such as 30°C) showed a thin film having smooth continuous texture (not insular structure), which was chemically active against oxygen.

鉄-亜鉛合金電着における析出組成と電解条件について

The electrodeposition of Fe-Zn alloys was interested in the properties of deposits and the mechanism of their deposition. Although many works have been contributed to the studies on this deposition, its mechanism has not yet been clarified.Standard single electrode potential of Zn in single salt solution is less noble than that of Fe. However, it was noted that Zn preferentially deposits under a certain plating condition. It suggests that the type of these alloys is formed by anomalous codeposition.In this paper, the effects of plating factors upon the composition of the deposits from chloride solutions are investigated in order to clarify the mechanism of anomalous codeposition.The composition of these alloys was a function of many factors. The main factors included bath composition, total ion concentration of metals, current density, temperature, and pH of the bath. Transition current density for anomalous codeposition was determined by these results.On the other hand, it was found that there is a transition point of bath composition, at which the type of deposition changes from anomalous to regular. The point depended on temperature, but not on current density.

Potential and current distribution at electrodes with local variations of the polarization parameter

Calculations are communicated in order to estimate the effect of local variations of polarization on the local single electrode potential and the local current density in cells with plane electrodes.

Kinetics of Electrode Reactions

The use of absolute rate theory to predict rates of electrode reactions is discussed. It is shown that the rate of reaction at an electrode can be calculated from first principles if the absolute single electrode potential and its temperature coefficient are known. The single electrode potential can indeed be calculated and therefore used to predict the exchange current density for any electrode reaction. Exchange current densities calculated from first principles for various mechanisms in the oxygen and hydrogen evolution reactions are in good agreement with the presently accepted mechanisms.

Oxygen Generation by a Novel Electrochemical Method

The present oxygen generating apparatus comprises as the cathode a porous air diffusion electrode commonly employed in fuel cells, while the anode consists of a nickel plate. When air is supplied to the cathode, the oxygen contained is reduced to OH- ion and transported through the electrolyte to the anode, where it is recovered as oxygen gas. In this process, the single electrode potential at the anode is of the same value as in the case of electrolysis of water. On the other hand, however, the cathode potential for reducing O2 to OH- is nobler than that for reducing H+ to H2 in water electrolysis. Consequently the overall potential between the electrodes takes a lower value than in the electrolytic process. The experiments lead to the conclusion that the power consumption is of the order of 2 KWH/M3 of O2 obtained, approximately one fifth of what is normally required in the electrolytic process. With further improvements in air diffusion electrodes, one may expect that the power consumption is substantially lowered to such an extent that the conventional fractionating process of air becomes obsolete.

Oxidation of sulfide ore bodies; II, Oxidation mechanisms of sulfide minerals at 25 degrees C

Measurements of the single electrode potentials of sulfide minerals backed with basic understanding of their electrode behavior make it possible to clarify their oxidation or reduction mechanisms. The electrode potential of a sulfide mineral is controlled by the first-step reaction of the oxidation mechanism for the sulfide in an oxidizing solution, and by that of the reduction mechanism in a reducing solution. Sulfides of copper, lead, silver, iron, and zinc were studied. The results indicate that the direct oxidation of a simple sulfide mineral is a process in which the metal atoms move into the surrounding solution to become aqueous cations, accompanied by a step-wise decrease in the metal to sulfur ratio of the remaining solid phase. When solid sulfur is finally left over, it undergoes a series of reactions to be oxidized to sulfate ion. In case of reduction, sulfur atoms move out into the solution to become aqueous sulfide ions with a step-wise increase in the metal to sulfur ratio of the solid phase. To illustrate, the oxidation of chalcocite proceeds as (Cu/sub 2/S) - 1/ 5(Cu/sub 9/S/sub 5/ + Cu/sup 2+/)r - (CuS + Cu/sup 2+/) - (2Cu/sup 2+/ + S). The path of the stepwise oxidationmore » is not necessarlly the same as that of the step- wise reduction for a metal-sulfur system. In the case of disulfides of iron, namely pyrite and marcasite, ferrous ions and S/sub 2/ molucules appear to be released simultaneously upon oxidation. (auth)« less

Contribution to the Theory of Cathodic Protection, II

The distribution of the electrical potential inside an electrolytic solution has been calculated for typical cases of cathodic protection involving an impressed current. In particular, it is shown under which conditions the differences in the local single electrode potential are sufficiently low so that complete cathodic protection without significant hydrogen evolution can be accomplished by using an automatic control of the impressed current.

Recent developments concerning the signs of electrode potentials

It is the purpose of this paper to review recent developments concerning the signs of electrode potentials, particularly with respect to single electrode potential, half-reaction potential, and half-cell electromotive force.

Advances Toward a Stable Sensitive Iron Dosimeter

Utilization of the conventional ferrous sulfate dosimeter indicates the desirability of a chemical system which exhibits greater stability and is more sensitive to energy absorbed from radiation. Greater apparent sensitivity has been achieved (a) by comparing with a potentiometer the single electrode potentials of irradiated against unirradiated solutions, (b) by concentrating the ferric ion in a solution on an ion exchange column, and (c) by using aqueous solutions other than that proposed by Fricke. The potentiometer method is somewhat more difficult than that using the DU spectrophotometer and has not been exploited. The column concentration is successful, although in at least one case the resin in the column appears to cause a small amount of oxidation of ferrous to ferric ion. Most of our work to date is concerned with other solutions. A cursory examination of many metal cations showed that iron exhibited the greatest sensitivity and it has been adopted throughout. To stabilize the system, additive chemicals have been sought which would form complexes both with ferrous and with ferric ions. Addition of inorganic anions generally produces a dosimeter not more sensitive than that of Fricke. Addition of organic acids can produce a dosimeter of greater or lesser sensitivity, apparently depending on the groups contained in the acid, as well as on spectral considerations. Some of these dosimeters also exhibit long-term stability. Our current standard has a G of 40 or so and has exhibited no observable change in the absence of irradiation since being mixed in June 1956. The composition is as follows: To 1 N H2SO4 add 7 × 10−4 molar benzoic acid and then 7 × 10−4 molar Fe+2 as FeSO4. The optical density is read at 2715 Å. Having stabilized the ferrous system, for example with benzoic acid, further additions of aliphatic organic acids can increase or decrease the sensitivity. Oxalic acid (1.5 gm./liter) gives a G ∼ 60. Tartaric acid (0.4 gm./liter) can give G ∼ 130 under suitable conditions. There appear to be drift considerations with systems investigated to date when G > 45. Wavelengths of absorption and transmission, pH range to provide known complexing and to keep the iron from adhering to container walls, temperature control of solutions, and the kind of groups being added are all items of importance. Some insight is being gained as to the effect on sensitivity of some of the functional groups in the additive organic acids.

Corrosion and Corrosion Research

The elements of the corrosion cell are described and it is demonstrated that a great variety of half-cell reactions are possible whose single electrode potentials can be computed from thermodynamic constants and the composition of water. It is shown that only those half-cell reactions which produce the greatest electromotive force can occur. The method if identification of the half-cell reactions for a particular case is illustrated. It is shown that the theory can be used to great advantage in selecting water-treatment processes for corrosion control. The theory underlying the correct procedure for polarization tests is developed, and it becomes evident that all unknowns can be evaluated if the single electrode potentials are computed first.

THE CHEMICAL CORROSION RESISTANCE OF COMMERCIALLY PURE TITANIUM AND THE INFLUENCE OF ITS CARBON CONTENT ON THE PROPERTY

The influences of carbon content on the various properties of commercial pure titanium have been studied in our laboratory, and the report on the effects of carbon on the mechanical properties, fabricating properties and heat treatment properties was already published in the "Light Metals", No. 12 (Aug., 1954 issue).This paper reports on the influence of carbon on the chemical coroosion resistance on the commercially pure titanium.Titanium, which has excellent chemical corrosion resistance, is being utilized as a construction material in the field of chemical, petroleum and synthetic fibre industries in the place of the conventional corrosion resistant metals such as stainless steel, stellite and hastelloy. And reflecting the situation, various reports on the chemical corrosion properties of titanium have already appeared in domestic and foreign literatures.We, also, conducted experiments on the property using the commercially pure titanium which was produced in our plant. Compared with previous papers on corrosion properties, our report is characterized in the following points:(1) The influence of carbon on the corrosion properties was studied.(2) The standard single electrode potential of titanium and other metal was calculated, and the corrosion resistance of titanium was examined from that view point.(3) The hydrogen and oxygen contents in specimens were analysed by the N. R. C. vacuum fusion gas analysis apparatus before and after dipping test.As the result we obtained the following conclusion:(1) Kobe Steel Work's titanium has excellent corrosion resistance against almost all chemical reagents except the following cases: a. HCl 20°C, >90%; boil, >1% e. AlCl3 boil, >25% b. HF f. Oxalic acid boil, >0.5% c. H2SO4 20°C, >70%; boil; >1% g. Formic acid boil, >25% d. H3PO4 boil, >10% h. Trichlor acetic acid 100°C 100%(2) Carbon content in the specimens has no influence on the corrosion propreties when in the range of 0.05-0.12%.(3) As the result of theoretical calculation of the standard single electrode potential, it was clarified that the position of titanium in the ionization series was between aluminium and zinc.(4) By means of gas analysis by the N. R. C. vacuum fusion gas analysis apparatus it was confirmed that-a. When titanium was dipped in the nonoxidizing acid such as HCl or H2SO4, the hydrogen content in the specimens increased remarkably, while oxygen content after dipping was nearly equal as before dipping.b. When titanium was dipped in the oxidizing acid such as HNO3, both hydrogen and oxygen contents did not increase and kept the original value.

STUDIES ON THE CORROSION OF ALUMINIUM AS AFFECTED BY ITS SURFACE TREATMENT

The NaCl single electrode potential of aluminium refered to IN calomel cell in NaCl aquores solution as affected by its surface condition was studied by specially made vacume tube potentio meter (fig. 1). Potential of aluminium varies largely by its surface treatment. The potential of aluminium with its natural oxide film is nobler then the case when its film was removed by special treatment as electrolytic polishing in acetic unhydrat and perchloric acid bath. The specimen with no oxide film show special corrosion behavior in acid and alkali solution as shown in fig. 4. But its oxide film groth rapidly when the specimen was dried or immersed in mater which contains oxygen.

ON THE DISCOLOURATION OF ALUMINIUM SURFACE IN BOILING WATER (PRAT 2)

In the Part 1 of this report, we discussed about the conditions in which the discolouration occurres and summarized them in three simple items. In this part, we intended to solve this phenomenon by comparing the sample which is boiled in distillated water (not discoloured) with that boiled in well water (discoloured).The analyses of well-water indicate that PH is 7.5, alkalinity is 301.24ppm, acidity is 17.2apm and iron ion is 0.17ppm. In comparison with this data, the analyses of service-water of Sakai City show that PH is 7.1, alkalinity is 50ppm, acidity is 3.0ppm and iron ion is 0.05ppm.Photo. 2 are the electron diffraction photographs of the surface of aluminum. No. 1 shows the photo. of the bare aluminum before boiling. No. 2 shows the photo. of the bare aluminum which was polished and etched in 20%HNO3. No. 3 shows the photo. of the surface of aluminum after boiling in the well-water. No. 4 shows that after boiling in the distillated water. In comparison No. 3 with No. 4, we found the remarkable difference, but from this photographs we could find no clew of discolouration. We detected, however, that the crystalline alumina was formed on the sarface of aluminum which was boiled in the distillated water.From the results of the Part 1 and the analyses of well-water, the factor of discolouration seemed to be the iron ion included in the well-water. Then, we examined the discolouration of the samples that was boiled in the distillated water in which the small amount of FeSO4 or FeSO3 was contained. The results was negative as shown in Photo. 3. Namely, no discolouration was occurred before the concentration of iron ion reached to 1, 000mg/l. As the concentration of iron ion is 0.17mg/l in the well-water, however, the discolouration seemes to be not the simple action of iron ion as above experimeht, as if iron ion may be the factor of discolouration.Moreover, the next experiment certainly indicates that the mechanism of the discolouration is not the simple substitution of iron ion for aluminum ion. The experiment included that two aluminum samples were immersed in the well-water and conected to the each pole of the D. C. source (1V and 2V) and then boiled for 1 hour. For the results, the anode aluminum is more blackened than cathode one as shown in the Photo. 4. From this results, the discolouration seems to occur rather by adsorption than by substitution.We measured the single electrode potential of samples refered to Pt and solutional current in boiling distillated water and well-water, etc. Fig. 1-4 shows the results. From this curve also, we could not yet point out the factor of this phenomenon.Finally, we examined the corrosion resistance of the samples which were boild in the distillated water and well-water. Thee results are shown in Fig. 5-7. From this results, it seems to be say that the sample boiled in the distillated water is most resistant to any corrosive solution but the discoloured sample boiled in the well-watter is more resistant to the alukali solution than the bare aluminum, although it has the lowest resistance to the acid solution and 3%NaCl solution. From these facts, again, it seems to be reasonable to suppose that the blackning factor may be the iron ion.

酸性河水を使用する水力発電所における腐蝕ならびに防蝕の研究（第4報）電気化学的研究（そのI）流水による腐蝕

In the present investigation, the mechanism of corrosion by flowing acid river water was studied. The effect of relative movement between electrode and adjacent solution and the effect of difference of pH of solution on the single electrode potential, the potential of corrosion cell, the anodic polarization and the cathodic polarization were investigated on mild steel, stainless steel and gun-metal in sulfuric acid solutions of which pH was in a range from 6.0 to 3.0. Violent corrosion is caused by acid river water even at the velocities at which the erosion does not break forth. According to author’s experimental results, the cause is manly due to the depolarization reaction,and acid river water becomes very corrosive when the pH decreases lower than the range from 5.5 to 5.0.

熔射金屬の電氣化學的性質 (1) 熔射銀の單極電位

The single electrode potential of sprayed silver was measured as accurate as possible and was found that the potehitall was in general a little lower than that of the ordinary silver, though it is greatly influenced by spraying methods and conditions. As a reference, we also measured the electrode. potential of electrochemically deposited silver and cold worked silver, and, found that the latter was usually a little less noble than the annealed normal silver. These results lead us to conclude that the sprayed silver has some internal stress as we predicated in our X-ray investigation of sprayed metals. By further experiments, it was also found that the internal stress can be removed by proper annealing or even by allowing the sprayed silver more than two weeks at room temperature.

Temperature coefficients of single electrode potentials

Temperature coefficients of single electrode potentials

A valve potentiometer

The usual thermionic valve circuits for amplifying the small measuring current in potentiometric methods cause serious errors due to the appreciable grid current present in valves having high mutual conductance. On the other hand, the use of electrometer valve is attended with lack of sensitiveness. A d.c. amplifier has been described using an electrometer triode coupled to a valve of LP2 type. The drift was considerably less than in a single valve circuit and electrode potentials could be measured to 0·1 millivolt using a unipivot galvanometer. A simple high-insulation switch is designed which enables both the standard and secondary cells to be operated with ease.