In the previous report, the anodic behaviour of lead alloy anode for cathodic protection was studied in high temperature sea water of gas condensers at 44 to 52°C and also in the normal temperature sea water at a sea-water intake.
In this report, the corrosion resistance of lead alloy anode in high temperature sea water at 74 to 46°C and at high current density of 3 to 5A/dm² was tested.
The results obtained are as follows:
1) Lead-silver (4%)-antimony (1%), and lead-silver (3%)-antimony (1%) alloy anodes were practically applicable to the high temperature sea water up to 70°C and at current density of 5A/dm².
2) The main component of the film formed on lead alloy anode was β-PbO₂ in nearly neutral (pH 8) seawater

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The pit growth of austenitic stainless steels in 5% NaCl aqueous solution at 70°C was investigated electrochemically by an artificial pit method.
Since the pit growth depends mainly on the macrocell formed inside and outside a pit and an artificial pit method can separate the macro-anode from the cathode, this method is the most suitable for the quantitative study of this process.
The artificial pit specimen used in this experiment consists of two disks of the stainless steel to be tested sandwiching a sheet of Teflon in a Teflon holder, and has advantages of easiness to make and less appearing of the crevice corrosion. The inside surface of the artificial pit was activated galvanostatically with anodic current prior to electrochemical measurements.
Measurements conducted were the potentiostatic anodic polarization of the pit, dissolution current in natural pit growth, and so on. The corrosive medium formed during the pit growth was assumed from comparison of the anodic polarization curve of the pit with those in the model solutions made from. HCl and NaCl.
Pit growth rate due to the macro-cell mechanism was shown to be 10²-10⁴ (-10⁵)μA/cm² in this environment and when the cell circuit was open the rest potential of the pit was about -0.25V vs. SCE. During the pit growth the concentration of hydrogen ion in the pit changed to at least N/100 and that of chloride ion to about 5N.
Comparison of anodic polarization curves suggested that the dissolution of the pit took place through a kind of unstable film in the highly concentrated chloride solution of low pH.

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In the previous report, a new method of precipitation of hydrated iron oxide by interfacial reaction between concentrated ferric-ferrous salt solution and sodium hydroxide solution was described. The fact that the addition of small amounts of CuCl₂ to FeCl₃^- FeCl₂ solution depresses the growth of spinell type oxide in the reaction product called ‘artificial rust’ was also reported.
In the present paper, the change of specific surface area and a related change of the property of the artificial rust by the addition of CuCl₂ is described.
Specific surface area determined by the BET method is larger for the artificial rust formed from the solution containing CuCl₂. This effect becomes remarkable when the amount of CuCl₂ added exceeds 1mol%.
The amount of water adsorbed on the artificial rust at 30°C and 100% relative humidity is also larger for the rust made from the solution containing Cu (II).
Determination of specific surface area of natural rusts was carried out with steel samples exposed in urban and industrial atmospheres. The result showed that the specific surface area of the rusts produced on low alloy steels was somewhat larger than those on ordinary steels.
On the basis of these experimental findings and other known facts, the protective nature of rust layers is discussed.

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