The corrosion tests on iron-nickel alloys were carried out in malefic acid solution and the results obtained were summarized as follows:
(1) The polarization for anodic dissolution of active alloys became larger as nickel content increased.
(2) The rise of temperature increased remarkably the anodic dissolution and the corrosion weight loss.
(3) The natural electrode potential of the α phase alloys containing less than 30% Ni was found to be about 0.1V less noble than that of the γ phase alloys containing more than 30% Ni in maleic acid solution.
(4) Two stages were distinguished in the polarization of the alloys containing less than 30% Ni: the first is the dissolution of the α phase and the second is the dissolution of the γ phase.
(5) The formation of the order lattice (FeNi₃) in the alloys was not always to increase the corrosion resistance of the alloys.

View full abstract

In order to investigate the effects of cathodic protection on steel surface exposed in tidal zone, the following tests were conducted with mild steel plates.
Correlations between immersion time ratios (to total exposure time) and protective effects were investigated for steel plates, of which the potentials were kept within three ranges of -900mV- -1, 000mV, -1, 000mV-1, 100mV and -1, 200mV with reference to sea-water Ag/AgCl electrode by coupling them to galvanic anodes of Zn, Al and Mg.
Protective effects were calculated from the difference of weight losses between protected plates and unprotected ones.
Results obtained are as follows.
1) The protective effects are 95-98% in all the three potential ranges, if the immersion time ratios are above 95%.
2) The average protective effects are 50-60% if the immersion time ratios are within the range of 40-90%, but the more negative the potentials, the higher the effects.
3) The protective effects are much smaller if the immersion time ratios are below 40%, but in the potentials of -900mV- -1, 000mV the effects are comparatively higher, and so it is necessary to use other corrosion control associated with cathodic protection especially in these environments.

View full abstract