The meanings of the study of passivation phenomena are discussed in relation to the surface finishing on iron & steel. Anodic passivation of iron in 10% HNO
3 & 10%H
2SO
4 solutions, especially the effects of magnetic field are studied.
1) 10%HNO
3: In the magnetic field perpendicular to the anode plate, the passivation time is prolonged, but in weak magnetic field parallel to the anode it is rather quickened.
The passivation films made in the magnetic field above 200O
e are resistant to 10%HNO
3 after switched off the current.
2) 10%H
2SO
: In the case of ordinary vertical electrode, two steps of passivation are found: the first one is accounted for by the black Fe
3O
4 film which grows thick, the second one by the same transparent film of γ-Fe
2O
3 as that in HNO
3. The effects of the magnetic field have the same tendency in both perpendicular & parallel magnetic field. That is, the Fe
3O
4 passivation time is not effected and γ-Fe
2O
3 passivation time is delayed.
In the case of horizontal electrode, it is passivated muchmore readily, and in general only γ-Fe
2O
3 passivation is occured. The effects of magnetic field are just like the case in 10%HNO
3.
The films made, also in magnetic field, are weak.
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