340 SECTIONAL TRANSACTIONS.— B. 



baths, some simplification of the older ' formulae ' has been effected, and it 

 has become possible to exercise a much more exact control over conditions 

 of operation, and hence over the character and properties of the deposit. 

 A better understanding of the influence of effective acidity (pH value) on 

 the conditions of deposition, especially of nickel, has been vital to securing 

 sound deposits of adequate thickness under modern conditions of mass 

 production. The study of the factors enabling the plating process to 

 penetrate into recesses in the object to be coated, instead of occurring unduly 

 preferentially on projecting regions nearest to the anode, has led to the 

 production of solutions for which this ' throwing power ' is high enough 

 to permit the deposition of a reasonably even coating on articles of compli- 

 cated shape. Investigations on the effects of ' addition agents ' of various 

 kinds — especially colloids and other substances of high molecular weight — 

 have resulted in the production of smooth, coherent coatings from solutions 

 which otherwise yield coarsely crystalline, irregular, or spongy deposits ; 

 and are now leading to the direct production of coatings so lustrous as to 

 eliminate the need of polishing — a matter which may be of special im- 

 portance when the size or shape of the article, or the properties of the deposit, 

 render the polishing process difficult and costly. 



Exact correlation of conditions of deposition with the character and 

 properties of the deposit requires the provision of quantitative tests of 

 properties of the coating such as hardness, porosity, internal stress and 

 adhesion ; the introduction of such tests has furnished important informa- 

 tion which enables these properties to be accurately controlled in practice 

 and has led to developments in the use of electrodeposition for special 

 purposes such as the electroforming of sheet and tube, the building up of 

 worn machine parts and the provision of a hard facing on gauges, press 

 tools, printing cylinders, etc. A further stage consists in correlating these 

 properties with the crystalline structure of the deposit. Microscopical 

 examination of etched surfaces and sections has done much to indicate the 

 size, shape and general arrangement of the crystallites of which the deposit 

 is built up, and even to detect the presence of non-metallic matter — e.g. 

 oxides — which, entering the deposit in a colloidal state, may profoundly 

 modify its crystalline character. Problems in this field involving the actual 

 nature of adhesion of electrodeposits and the manner in which their structure 

 is built up are also being attacked by X-ray examination and more recently 

 by electron diffraction methods. 



The striking improvements which have been made — especially during 

 the last ten to fifteen years — in the control of the whole plating process, 

 including the very important preliminary cleaning operations required to 

 free the surface of the basis metal from traces of grease or other impurities 

 which would prevent perfect adhesion of the coating, have raised the general 

 standard of quality and reliability of plating to a remarkable extent and 

 given users a real confidence in its value for a wide range of new industrial 

 purposes. The resulting increase of demand has stimulated the introduc- 

 tion of mass-production methods for plating articles in automatic plants ; 

 the articles to be plated are carried at a regular rate by conveyor chains 

 through a succession of tanks and chambers in which the operations of 

 cleaning, washing, plating, rinsing and drying are conducted in their proper 

 sequence and each for its appropriate time ; such plants have become a 

 feature of modern electroplating industry. An automatic nickel-plating 

 plant may carry 3,000-5,000 gallons (or even more) of solution and as much 

 as 5 tons of nickel anodes. It is estimated that the total area covered by 

 nickel plate alone amounts to 250 million sq. ft. per annum. 



Progress along the lines indicated may be expected to continue in the 



