To investigate the chemical factors which influence the sulfide corrosion cracking of storage tank materials for LP gas, hydrogen absorption which is responsible for the cracking was measured on samples of a high strength steel together with measurement of the corrosion rate; the samples were exposed to different corrosion environments, such as a saturated aqueous solution of hydrogen sulfide, a hydrogen sulfide stream saturated with water vapor, and LP gases with and without liquid water (or water vapor) containing sulfides, and then the amount of hydrogen evolved by heating the samples at 170°C was measured.
The volume of hydrogen absorbed was much more in the steel treated in liquid water saturated with hydrogen sulfide than in the steel treated in hydrogen sulfide gas saturated with water vapor. In every one of LP gases, propane, butane, and propylene, the steel was corroded in almost the same degree and absorbed a great amount of hydrogen when the LP gases contained hydrogen sulfide and water in liquid state. Any hydrogen was scarcely absorbed when propane contained hydrogen sulfide and water in vapor state. No hydrogen absorption was found in tests made with propane containing methyl mercaptane and liquid water.
It is consequently concluded that water plays an important role in the hydrogen absorption and that the simultaneous presence of hydrogen sulfide and liquid water is a requisite for accelerating the hydrogen absorption.

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The atmospheric corrosion rates of steel were measured in an industrial district (Kôtô-ku) of Tokyo, Japan.
Analyzing correlations between the corrosion rates and meteorological factors and/or atmospheric pollution substance factors by means of statistical analysis method, a corrosion regression was obtained to describe the influence of these two mutual interacting factors on corrosion of steel.
The result may be expressed as:
y=-136.91+0.05x₁+2.56x₂+0.12x₃+3.60x₄+(-24.63)x₅+2.0x₆+(-14.37)x₇+13.43x₈+3.65x₉+(-1351.99)x₁₀
where,
y: corrosion rate (mdd), x₁: temperature (°C),
x₂: humidity (RH%), x₃: precipitation (mm),
x₄: sulfur dioxide (mg/day·100cm²),
x₅: sea-salt particles (chlorides) (mg/100cm²),
x₆: wind velocity (m/sec), x₇: soluble substances (g),
x₈: insoluble substances (g), x₉: sulfates (g),
x₁₀: tar substances (g).

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