1875年：Nature发表的关于“氢脆”的文章

2024-11-27 14:49:56 作者：本网发布来源：考拉腐蚀分享至：

【文章题目：On some remarkable changes produced in iron and steel by the action of hydrogen and acids】

For a long time, it has been well known to wire drawers and other manufactures, who free the iron or steel they are engaged in working from rust by cleaning it with sulphuric acid, that after this process the metal becomes much more brittle than before. Further, if a piece of iron wire that has been cleaned in sulphuric acid be bent rapidly to and fro till it is broken, and the fracture be then moistened with the tongue, bubbles of gas arise from it, causing it to froth. If this same wire be now gently heated for a few hours, or left in a dry warm room for some days, it will be found to have regained its original toughness, and not to froth when broken and the fracture moistened.

Some experiments made by the writer on this subject during the last three years, have showed that not only sulphuric, but hydrochloric, acetic, and other acids which give off hydrogen by their action on iron, produce the same effect, making it probable that hydrogen is the cause of the change. This view is confirmed by collecting the gas given off at the surface of the iron and burning it when the characteristic flame of hydrogen is seen.

Putting the facts together, it seems probable that a portion of the hydrogen generated by the action of the acid on the surface is occluded and subsequently given off, either rapidly, as when the iron is heated by the effort of breaking it causing the water on the surface of fracture to bubble, or, more slowly, in the cold.

Perhaps the simplest way of charging a piece of iron with hydrogen is by laying it on a sheet of zinc in a basin of dilute sulphuric acid. An electric current is here set up, and the hydrogen generated by the action of the acid on the zinc is given off at the surface of the iron. In this way two minutes or even less will often suffice to charge a piece of iron with hydrogen and alter its properties as completely as one hour’s immersion in dilute acid without the zinc.

The change in the properties of iron which has occluded hydrogen is not confined to a diminution of toughness, though this may be reduced to one-fourth, but is accompanied by a remarkable decrease in tensile strain, amounting in cast steel to upwards of twenty per cent, after 12 hours’ immersion in suphuric acid. With iron wire the decrease in tensile strain was found to be less than with steel the reduction amounted however in some cases to six percent. Some interesting differences are noticeable in relative effect of occluded hydrogen on mild steel and highly carbonised steel, the dimimution of tensile strain after occlusion of hydrogen being greater in the latter case than in the former.

As with the metal paladium, so with iron, the electrical resistance is increased somewaht by occlusion of hydrogen; in face, it seems probable that every property of iron or steel undergoes a change after the occlusion of hydrogen, and the extent of this change becomes a matter of great interest to the engineer now that iron and steel are so largely used.

Cases of the deterioration in toughness of iron of excellent quality exposed to the action of gas containing acid, as in the upcast shaft of a coal-pit, have come before the writer’s notice, in which the change appeared to have resulted more from hydrogen occluded by the iron than its corrosion by the acid vapours. It is also probable that rapidly rusting iron occludes hydrogen, and is thereby weakened in strength and toughness.

William H Johnson.

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