Nickel alloys curves

Anodic polarization curves for chromium-nickel alloys in 1 N H2S04. Redrawn from Ref 1 3... 

The curves relate to the behaviour of aluminium brass and of the 90 10 and 70 30 copper nickel alloys in artificial sea water at pH 8.2 and a temperature of 40 °C. The surface area of the electrodes was about 33.7 cm, while the sea water flow rate was 1.0 ms. The geometry of the three electrolytic cells was the same. 

Figure 21-11 gives a depth profile for the copper-nickel alloy described in the previous sectitrn (Figure 21-8). Here, the ratios of the peak intensities for copper versus nickel are recorded as a function of sputtering time. Curve A is the profile for the sample that had been pa.ssivated by anodic oxidation. With this sample, the copper-to-nickel ratio is essentially zero for the first 10 minutes of sputtering, w hich corresponds to a depth of about SO nm. The ratio then rises and approaches that for a sample of alloy that had been chemically etched so that its surface is approximately that of Ihe bulk sample (curve C). The profile for the nonpassivated sample (curve B) resembles that of the chemically etched sample, although some evidence is seen for a ihin nickel oxide coating.

Figure 6.14. Values of critical and passive current densities obtained from potentiostatic anodic polarization curves for copper-nickel alloys in N H2SO4, 25°C [42]. (Reproduced with permission. Copyright 1961, The Electrochemical Society.)...

Ponthiaux P., Wenger F. Galland J. (1995). Study of the anodic current-voltage curve of an iron-nickel alloy in normal sulfuric acid. Journal of the Electrochemical. Society., Vol. 142, No. 7, pp. (2204-2210), ISSN 0043-1648. 

The O2 reduction on Ag [28,64,65], Ni [66], and Ni-Ag alloys [66] was studied with the ring-disc assembly in recent years. The i — U curves in Fig. 80 were measured [66] at 1000 rotations/min on the disc in 0.1 M KOH. The disc was made of silver for curves a and a and of nickel for curves b and b. The disc surface was polished mechanically with quartz powder and subsequently polarized cathodically for curves a and b (prereduced electrodes). Anodic polarization with lOmA/cm for 2 min served as the pretreatment for curves a and b (preoxidized electrodes). The curves a, a, and b are similar in shape to the i — U curves on platinum metals in Fig. 72. The net process is limited by the O2 diffusion at I/<0.4V. The decrease of / with increasing potential occurs on prereduced nickel in the potential range where the surface... 

The O2 reduction was investigated [66] on silver-nickel alloys prepared by pressing appropriate amounts of silver and nickel powder under heat. The porosity of the pressed electrodes was between 3 to 5 %. The current measured [66] in 0.1 M KOH at 0.5 V or 0.1 V with 1000 rotations/min is plotted in Fig. 81 as a function of the silver content for preoxidized discs made of different alloys. The increase in the reactivity of the alloys with silver content is greater below 40% than would be expected on the assumption of an additive superposition of the currents of the pure components according to the bulk composition. The currents for additive superposition are shown by dotted lines in Fig. 81. Above 50% the reactivity of the alloys is comparable to that of silver. The cause of the shape of the curves in Fig. 81 is not known with certainty. It is conceivable that the surface layers are richer in silver than the bulk. 

Corrosion Rate by CBD Somewhat similarly to the Tafel extrapolation method, the corrosion rate is found by intersecting the extrapolation of the linear poi tion of the second cathodic curve with the equihbrium stable corrosion potential. The intersection corrosion current is converted to a corrosion rate (mils penetration per year [mpy], 0.001 in/y) by use of a conversion factor (based upon Faraday s law, the electrochemical equivalent of the metal, its valence and gram atomic weight). For 13 alloys, this conversion factor ranges from 0.42 for nickel to 0.67 for Hastelloy B or C. For a qmck determination, 0.5 is used for most Fe, Cr, Ni, Mo, and Co alloy studies. Generally, the accuracy of the corrosion rate calculation is dependent upon the degree of linearity of the second cathodic curve when it is less than... 

These relays also possess characteristics similar to those of a bimetallic relay and closely match the motor heating and cooling curves. They are basically made of a low-melting eutectic alloy which has defined melting properties. The alloy, with specific proportions of constituent metals such as tin, nickel and silver, can be made for different but specific melting temperatures. This property of the alloy is used in detecting the motor s operating conditions. 

Since the rate of formation of cementite is determined by nucleation, and therefore proceeds more rapidly in fine-grained steels, it follows that the T-T-T diagram will show a more rapid onset of austenite decomposition than in steels of the same composition, but a coarser grain size. The shape of the T-T-T curve is also a function of the steel composition, and is altered by the presence of alloying elements at a low concenuation. This is because the common alloying elements such as manganese, nickel and clrromium decrease... 

Fig. 3.36 Effect of nickel on the anodic behaviour of iron alloys in 1 N H2SO4 at 25°C. Curve 1 Fe curve 2 Fe-lONi Curve 4 Ni (after Beauchamp )...

Thompson and Tracy carried out tests in a moist ammoniacal atmosphere on stressed binary copper alloys containing zinc, phosphorus, arsenic, antimony, silicon, nickel or aluminium. All these elements gave alloys susceptible to stress corrosion. In the case of zinc the breaking time decreased steadily with increase of zinc content, but with most of the other elements there was a minimum in the curve of content of alloying elements against breaking time. In tests carried out at almost 70MN/m these minima occurred with about 0-2% P, 0-2% As, 1% Si, 5% Ni and 1% Al. In most cases cracks were intercrystalline. 

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