Amorphous Ni-Cr-P-B alloys, which possess a high corrosion resistance and are apt to form the amorphous structure, have been prepared by rapid quenching from melts. The alloys containing chromium of 7 and 9at.% are not corroded in 10% FeCl₃·6H₂O at 30°C. Spontaneous passivation occurs on these alloys in 2N H₂SO₄ and 1N HCl, and a critical potential for pitting is not observed on the anodic polarization curves even in 1N HCl. Simultaneous determination of the thickness and composition of a passive film and the composition of the surface of substrate alloy directly under the passive film has been carried out by X-ray photoelectron spectroscopy. The passive film formed in 2N H₂SO₄ consists mainly of hydrated chromium oxy-hydroxide similar to those formed on corrosion-resistant crystalline alloys containing chromium and the composition of the surface of substrate alloy directly under the film is not different from that of bulk alloy. On the contrary, the composition of passive film formed in 1N HCl can be expressed as (Ni^II_0.26Cr^III_0.74) (PO₄)_0.74O_x (OH)_0.52-2x (1.74+x) H₂O and hence phosphate comprises 81% of constituents of the passive film. In addition, the composition of the surface of substrate alloy directly under the film changes from that of bulk alloy. In conclusion, the amorphous Ni-Cr-P-B alloys with chromium of 7 to 9at.% have a high corrosion resistance in strongly acidic solutions and the great resistance to pitting corrosion, but may not be always stable for a long time because of the change in alloy composition directly under the film.

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The distribution of the protective current on the propeller of FRP ship was estimated by using the comformal mapping, with reference to the cathodic protection of the propeller by the zinc sacrificial anode. The resistance between the propeller and the zinc anode was calculated by transforming the propeller into an equivalent ellipsoid. The current distribution on the ellipsoid was drawn by the conformal mapping, and the arrangement of zinc anode for an uniform current distribution on the ellipsoid was discussed. As the result, it was found that an uniform current distribution would be obtained by providing three zinc anodes on hull bottom, redder and overhang.

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The inhibition mechanism of adsorptive inhibitors was explained by considering some factors influencing the inhibition effects, molecular coverage area, electron density, steric hindrance, adsorption center and extrinsic factors.

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In oil firing boilers, the acceleration of high temperature corrosive attack on superheater and reheater tubes caused by the presence of ash deposits containing vanadium, sodium and sulfur compounds are well known.
The paper described an example of corroded tubes, mechanism of vanadium and sulfidation attack, accelerated corrosion test and preventive methods of high temperature corrosion.

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