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The pyrophosphate bath has been found to be satisfactory for the plating of nickel. It gives good quality deposits over a wide range of operating conditions and has some advantages over the Watts bath.

The complex Sn2P~O7 bath was found satisfactory for the electroplating of Sn since it gave good quality deposits over a wide range of experimental conditions. Addition agents like dextrin-gelatin increased the brightness of the deposits. This bath has several advantages over the stannate bath.Acid sulfate and alkali stannate baths are widely used for industrial plating of Sn. In the literature, use of pyrophosphate baths is mentioned only by Roseleur (1-3) and Marino (4). Recently, Safranek and Faust (5) used the Sn~P~OT-copper cyanide bath for deposition of Sn-Cu alloys.The principal advantages of using pyrophosphate solutions for electroplating relate to high solubility, nonpoisonous nature, stability, and low metal ion concentration due to complex formation. Detailed investigations on the electrodeposition of various metals and alloys from this bath were undertaken to study the electrochemistry of metal pyrophosphate solutions, optimum operating conditions for satisfactory deposition, and to compare its performance with that of well-established baths. Electrodeposition of Sn, Zn, Cu-Sn alloy and Ni from the pyrophosphate bath has been reported briefly in preliminary notes from this laboratory (6-9). This paper presents in detail the work on the deposition of Sn.

Nickel has been codepositcd with cobalt from the pyrophosphate bath. Detailed studies on alloy composition, cathode efficiency, and potential have led to the optimum conditions for obtaining satisfactory alloy plates with 10-91% nickel. The efficiency of cast alloy anodes is quite high. X-ray patterns of the deposits show the existence of f.c.c, and hexagonal structures. The deposit composition could be altered appreciably only by varying the metal content of the bath.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.215.17.190 Downloaded on 2015-06-15 to IP Vol. 108, No. 1 ELECTRODEPOSITION OF Ni-Co ALLOYS 65 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.215.17.190 Downloaded on 2015-06-15 to IP

Weight losses of aluminum in hydrochloric acid are diminished in the ranges 16–75 for n-; 40–90 for di-n~ and 50–98percent for tri-n-butylamine. Inhibitor efficiency increases with acid concentration up to 1.25 or 1.5 N, depending on the inhibitor and is practically constant thereafter. Efficiency increases with increased inhibitor concentration up to a certain value, then remains constant. Optimum inhibitor concentration depends on acid concentration and immersion period. Experimental results indicate corrosion of pure aluminum in hydrochloric acid solutions is essentially under cathodic control and inhibition by amines is by adsorption on cathodic areas. A similar mechanism is indicated for aluminum alloyed with manganese.