For the purpose of using Pb alloy as an anode in cathodic protection, its corrosion behavior was investigated when soaked in the stagnant sulfuric acid solution without passing current.
The results obtained are as follows:
1) Corrosion rate of electrode can be expressed by sulfation time followed with a sudden change in natural electrode potential.
2) In relatively short period (24 hours), namely within the time just before the sudden change of natural electrode potential, corrosion resistance is decreased as the following order: Pb-Ag, Pb-As, Pb-Sb, Pb.
3) The amount of corrosion loss caused by long-term immersion does not follow the same order as stated above. This seems not due to simple film grown in the early stage of PbSO₄ formation, but to complicated surface covered by PbO and PbSO₄.

View full abstract

In order to investigate on cathodic protection of steel and stainless steel used for holding sulfuric acid, examination was conducted to check the behavior of pure lead, lead alloys and high-silicon iron in sulfuric acid solution. The experiments were done by measuring the anode potential and analysis of surface film by oxalatimetry.
The results obtained are as follows:
1) The growth rate of passive film on Pb, Pb-As, etc. follows parabolic law.
2) Those on Pb-Te, Pb-Ag, etc. follow the logarithmic law.
3) The amount of lead peroxide on Pb-Sn and Pb-Cd electrodes decrease in proportion to the lapse of time.
4) Allowable current density for Pb-Ag anode is considered to be approx. 10A/dm².
5) High-silicon iron may be used at the current density of 4A/dm², while its weight loss caused by corrosion reaches 0.05g/A·hr and is far larger than those of lead alloys examined.

View full abstract

The following items on moisture-proof packaging as corrosion preventive method for metal products, were studied:
1) The characteristies of moisture absorption of desiccants.
2) A convenient method for mutual conversion of moisture permeabilities under various atmospheric conditions.
3) Calculation of moisture permeability of barrier materials under variable atmospheric conditions.
4) Change of interior relative humidity of moisture-proof package.
Thus, an equation using parameters, i.e. quantity of desiccant, moisture permeability of barrier material and atmospheric condition, was specified in JIS-Z-0303 (General Rule of Rust Preventive Packaging Method).

View full abstract

Kraft papers containing various amounts of Cl^- and H⁺ were prepared in laboratry. A piece of the papers was put between two pieces of mild steel and the corrosive was tested under 40°C, 90% R. H. and room temperature. Corrosive action was evaluated by the measurement of rust degree of iron and steel specified by Japanese Industrial Specification.
Results obtained were as follows:
1) The allowable limit of Cl^- is about 0.4mg per 1g of material and beyond the limit, a proportional relation between Cl^- concentration and R was established, where R is rust degree of mild steel.
2) The allowable limit of H⁺ concentration is approx. 6 in pH and in acid range, log R is proportional to pH value.

View full abstract