The systematic researches on the mechanical properties of electrodeposited iron have scarcely been found. However, the above properties are very important factors for padding or being used for metallic materials. This paper reports the examination on the effects of pH, Fe⁺⁺ concentration, amounts of additives in the bath as well as the effects of bath temperature or current density on mechanical properties (such as hardness, tensile strength, elongation, reduction of area, and Erichsen value). The following sulfate bath was used for the examination.
FeSO₄⋅7H₂O……278g/l(2N)
pH……from 2.65 at the start to 2.95 at the end
Temperature of bath……75°C
Cathode current density……10A/dm²
(NH₂)CO, NH₄⁺, H₃BO₄, Mn⁺⁺, and Mg⁺⁺ were added to the bath as additives.
As the results, it was known that electrodeposited iron heated at 500°C indicated excellent mechanical properties over a wide range, some of which were almost the same as those of practical mild steel. In general, the largest elongation was obtained when the concentration of additive was 0.01N in the bath.

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Some observations were made under metallurgical microscope or electron microscope on the surface of the substrates pretreated by various processes and on the initial deposit of iron-nickel alloy thin film.
It was found that more suitable substrate surface for the basis of Fe-Ni alloy electroplating was obtained by thin copper electroplating than by mechanical or chemical polishing. Anomalous phenomena were observed at the early stage of Fe-Ni alloy electrodeposition. At the thickness of about 500Å, the deposited film contained a large amount of iron and the crystals dispersedly appeared. At the thickness of above 1000Å, the film approached to the average composition (Fe/Ni=20/80) with crystals of network structure.
These anomalous phenomena were also proved by the measurement of change in cathodic potential and by the analysis of the composition of deposited film.

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The bent strip method has been used by many investigators for measuring the internal stress in electrodeposits.
Although the formula, which they used for calculating the internal stress by the experiments of the above method, leads to a mean value of stress, it does not express the correct instantaneous internal stress, because the internal stress in electrodeposits always varys according to time and the instantaneous thickness of the deposit.
However, the authors presented a formula for calculating the instantaneous internal stress in the deposits, the formula could be applied for the experiments of the above method. The formula could express the instantaneous internal stress and transition point between compressive and tensile stresses exactly.
As the results of the evaluation of the behavior of internal stress in triple nickel plating, it was found that the semi-bright nickel as well as that obtained from watts bath showed tensile strength; while, the intermediate nickel from striking bath and bright nickel showed tensile strength at the initial stage of electrodeposition, but the direction of stress changed to compressive as the deposition proceeded.
Accordingly, it was concluded that the triple nickel plating was more profitable than single nickel plating in regard to the effects of internal stress in the electrodeposition.

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Experimental investigations were made on the effects of the addition of boric acid on the rate of deposition in various sorts of electroless nickel and cobalt plating baths containing a hypophosphite as a reducing agent.
Furthermore, the action of boric acid for promoting the deposition rate was evaluated in caustic alkaline tartrate cobalt plating solution which was remarkably affected by boric acid.
As the results, the following conclusions were reached.
1) Remarkable promoting effects of boric acid were observed in both nickel and cobalt plating baths containing only hydroxy-carboxylic acid such as citric or tartaric acide.
2) Cobalt tartrate complex dissolved in weak acid solution was converted into a type of less reducible complex in alkaline solution.
3) The relationship between the deposition rate and pH of bath was illustrated by the dependence of reducing force of a hypophosphite on pH and the above conversion of the complex in the solution.
4) The addition of boric acid to the plating solution promoted the plating reaction in the bath by the aid of its buffer action and complex forming ability.

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以上の全実験結果を要約すると次のようになる。
(1) アンモニア曝気法による耐食性試験は, 雰囲気温度とアンモニア濃度の規制によって良好な再現性を有し, 耐食性試験法として有効である。また簡単な応力試験法としても利用できる。
(2) アンモニア曝気法の適用基準および耐食性の判定基準は, メッキ製品の品質, 使用目的, 下地メッキの種類ならびにメッキ素材の種類などによって当然違いが生じるので, 十分検討されるべきである。
(3) 5μ程度の光沢ニッケルメッキの上にロジウムメッキ (1μ以下) をする場合, 耐食性は好ましくない。これはロジウムメッキの品質, 条件に関係なく, 下地ニッケルメッキ層に耐食性不良の原因があるからである。これを改善するには, 二重ニッケルが効果的で, 7μでかなり優れた耐食性が得られた。
なお本実験の過程で, メッキ素材自身に相当のピンホールがあって, これが耐食性に大きな重要因子となっていることが分った。また, メッキ素材の冷間加工や外力荷重などによる内部応力の増加現象が, あたかもメッキ層の内部応力が高いかのように現われることがあるので, いずれもメッキ素材の加工, 選択上大切なことがらの一つである。

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