The frequency change in EQCM was measured in an application to the monitoring of the thickness of nickel electroplating. The monitored thickness depended on the type of plating bath and the plating current density, which affected the stress in the plated film and the adhesive force between the gold film electrode and quartz. Mass sensitivity (Sm) in a simplified Sauerbrey equation, Δf=Sm·Δm, changed with the plating current density and the amount of plated metal. This result is related to the radial mass sensitivity of the EQCM electrode because plated nickel film was concave. Sm must therefore be determined experimentally.
Tin-antimony alloys were electrodeposited from acidic HEDP solutions containing 1-hydroxyethane-1, 1-diphosphonic acid (HEDP), stannous ions (Sn2+), antimony cations (SbO+), and ammonium ions (NH4+). Plating was conducted under the following conditions: 20±2°C, 2.0±0.1pH, and 10 to 50mA·cm-2 current density with weak agitation. The composition of the tin-antimony alloy deposits was affected by the pH, the metal concentration ratio in the solution, and agitation. The current efficiency tended to decrease with an increase exceeding 20wt % in the antimony concentration in the bath and antimony content of the alloys increased. The codeposition of tin-antimony alloys in a bath with a lower pH was found to be regular type because the antimony content of alloys was higher than that of antimony in the electrolyte. The codeposition changed to potential dependence with increasing pH in the bath, Sn-Sb alloy deposits containing Sb 20wt% to 50wt% were white in appearance and smooth.
Plating waste liquid collected for disposal from electroplating plants, contains large amounts of complex cyanide and organic matter in varying concentration so. Such liquid was conventionally treated using a boil-down method but this involved problems with the complex cyanide that remained in the resulting sludge and the high cost of treatment. We applied thermal-hydrolysis to treatment of such waste liquid and succeeded in decomposing the complex cyanide and removing the metal from it by adding two-step sulfide division to the process.
In a potassium sulfate solution, the polarization curves of silver electrodeposited from an electrolyte with different additives show that the amount of codeposited sulfur in the electrodeposited material increases with the amount of sodium thiosulfate. The current density thus increases in both the active dissolution region and the passive state. Adding, zinc ions, reduces both the amount of codeposited sulfur and the silver dissolution. Because of the codeposition of triethylene tetramine, the active dissolution of silver is also reduced. These phenomena, especially when triethylene tetramine, sodium thiosulfate, and zinc ions are added simultaneously, are especially interesting.
In a sulfite-system silver electroplating bath, the adsorption of additives onto the electrode is inhibited by the addition of zinc ions. The effects of the pH also decrease, while temperature greatly affects polarization curves. When sodium thiosulfate is added to the solution, the deposition potential shifts to negative, the limiting current density is lowered, and blight deposition layer is produced through the formation of sodium thiosulfate silver complex ions and multicomplex zinc ions. The deposition of zinc hydroxide and silver compound is also prevented. The electroplating bath thus becomes transparent and stable.
The corrosion-inhibiting effect of 1, 4-Di (thiocyanatomethyl) benzene on iron in pH 2 geothermal brine was investigated through weight-loss measurement at 150°C and electrochemical measurement at 50°C. Pitting corrosion and whole-surface corrosion on the iron were inhibited by the 1, 4-Di (thiocyanatomethyl) benzene, which increased the cathodic polarization and showed an excellent inhibition effect on steel tubes in two-phase flow geothermal brine.
Iridium oxide/titanium electrodes were prepared by thermal decomposition techniques from H2IrCl6 solutions containing silica sols and tantalum buthoxide, and subjected to an oxygen evolution reaction in acidic sulfate solutions containing an organic additive (ethylene chlorohydrine, ECH). The lifetime, T, of the electrodes was determined as a function of the number of coatings, n, current density, i, and the concentration of ECH, C. The variation of T with n is shown to be linear as a function of n2.3 for electrodes from silica sol solutions and of n for electrodes from the buthoxide solution. The lifetime also varied linearly with the reciprocal of the product i·C0.7 in the range C=10-2-3×10-1mol/L. It is thus possible to estimate the value of n for achieving T=8760h (a year) at C=10-3 mol/L by a combination of the linear relations between log T and log C, and log T and log n. The values of n thus obtained were 30 and 700 for solutions of silica sols and of tantalum buthoxide, respectively. Such an extension of the lifetime by the addition of silica sols far exceeds the expectations suggested by catalyst loading.