The performance of the three methods of accelerated corrosion tests, i. e., CASS, Corrodkote, and SO₂ tests must be in accordance with the following items.
(1) Similarity of corrosion defects in outdoor exposure tests.
(2) Accelerating properties in outdoor exposure tests.
(3) Reproducibility of the test results.
At first, the effects of the thickness of electroplated coatings under various corrosive atmospheres on the results of outdoor exposure tests were studied.
These three tests were carried out in view of comparing their characteristics in the above items (1) and (2).
The test revealed that CASS and SO₂ tests gave remarkably excellent results in the above items (1) and (2), and in respect to operation and expense.

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Chromic acid waste discharged from plating shops was treated with nitrites for the purpose of simpler disposal of the waste. The results of the above experiments were as follows.
(1) The rate of removal of chromic acid was proportional to the amount of NaNO₂ added, and it attained to nearly 100% at the addition of 30ml of NaNO₂ and 150ml of H₂SO₄ for 1l (1250ppm) of the chromic waste.
(2) The time of ventilation could be adjusted by the amount of H₂SO₄ added, and almost complete removal was obtained by 30min. of ventilations and 120ml of H₂SO₄ addition for 1l (1250ppm) of the chromic waste.
(3) The rate of removal was higher when the temperature of the waste was higher; however, the optimum temperature was determined on nearly 50°C from the standpoint of actual operation.
As the results mentioned above, it was found that NaNO₂ was a good reducing agent for reduction treatment of chromic acide waste.

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A novel method was proposed for producing the grinding wheel with single layer abrasives. It consists of the process of dipping steel base plate in nickel sulfamate bath, in which abrasive particles are suspended, and then, firmly bonding the particles by electroplating.
The process is so simple that any distribution densities and any depths of plated layer (in which abrasive particles are embedded) can readily be regulated.

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For the purpose of studying the effects of bonding conditions and determining the optimum condition, a series of grinding tests were carried out with the wheels having various depths of plated layer (in which abrasive particles are embedded) and distribution densities of abrasives, which had been prepared by the method in Part 1. The material used as abrasives was silicon carbide #150.
The maximum grinding power and the minimum wear of the wheel were obtained at distribution density of 90 particles/mm² and the ratio of depth (the ratio of depth of embedment to average shorter diameter of abrasive particles) of about 50%. Better bonding results were obtained when current density was rather low.

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It is important for the improvement of mechanical properties and corrosion resistance of the article to control the distribution of the plated metal on its surface. It is commonly known that alkaline bath always gives larger throwing power than acid bath. It is true in practice that distribution of metal produced by bright nickel bath is inferior to that by non-bright Watts' bath.
The authors studied on the control of throwing power by using a curved cathode in tank and investigated the effects given by brightening agents, surface active agents, bath composition, and operating conditions.
The following results were obtained:
(1) Addition of 1st class brightening agents hardly affect the throwing power. However, 2nd class brightening agents, except thiourea and gelatine, reduce the power and the reduction of the power is more remarkable when their amounts of addition are larger.
(2) Most of surface active agents improve throwing power, but they give lower values as seen in 2nd class brightening agents when their concentrations are excessively high.
(3) When sodium chloride, instead of nickel chloride, is added to Watts'bath, conductivity and throwing power of the bath are improved.
(4) In general, when current density is increased, throwing power is reduced. When air agitation is applied to the solution, throwing power is larger as compared with the case of no agitation.

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