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8 THE MARINE RECORD. OCTOBER II, Igoo, THE RELATIVE CORROSION OF WROUGHT IRON, SOFT STEEL AND NICKEL STEEL.* BY HENRY M. HOWE. This paper, of which the present as an abstract, gives the loss of weight by oxidation of many plates of wrought-iron, soft steel and nickel steel of 3 per cent. nickel and of 25 per cent. of nickel, when exposed to sea water, to river water, ‘ and to the weather for two periods of about one year each. Each plate was about 24 inches long, 16 inches wide, and one-eighth of an inch thick. The total weight of all the plates was 2,597 pounds, and the total area exposed was 928 _square feet. Thus the scale of the experiments was not only much larger than that of any previous experiments of which I know, but larger, I believe, than that of previous experi- ments taken collectively. The paper also tabulates and compares the results of all other accessible and respectable investigations into this subject. The general results are as follows: Wrought iron compared with soft steel. There is, at least in the United States, a strong and widespread belief that soft steel corrodes much more rapidly than wrought iron; and this belief has greatly retarded the introduction of soft steel for tubes for various purposes for which oxidation is a matter of vital importance. To this question, then, great attention was paid. We, of course, recognize a reasonably constant difference in tendency to oxidize, not only between metals much apart in their chemical properties, like sodium and platinum, but even between those which are far more nearly alike. We do not hesitate to say that manganese oxidizes more readily than iron, and iron more readily than copper. Between wrought iron and soft steel such a difference might exist, and there are many who suppose that it does exist that soft steel as a whole oxidizes more rapidly than wrought iron, just as iron oxidizes more readily than copper. But, while a difference of this kind might exist, I find no evidence in the data thus far collected that it does exist. I do not thus find that wrought iron as a whole corrodes more than soft steel as a whole, nor doJI find the reverse to be true. Taking all common classes of wrought iron and of soft steel together, and all conditions of exposure to oxida- tion to which engineering structures are commonly exposed, except, perhaps, in marine boilers, I find it extremely diffi- cult to say that either wrought iron or soft steel asa class on the whole excels the other in resistance to oxidation. But, while we find no marked difference between these two classes of iron taken as a whole, we often find moderate and somewhat constant differences in certain specific cases, and we sometimes find great differences. Thus in my own ex- periments soft steel corroded less than wrought iron in fresh water, but more than wrought iron in sea water; and the difference, though always moderate, was in each case suffi- ciently constant to raise a considerable presumption that it was areal and not merely an apparent one. But, though soft steel in sea water thus corroded more than wrought iron in my experiments, it corroded much less than the wrought iron in Krupp’s very important experiments; and here, too, the difference was so constantas to raise a considerable pre- > sumption that it is real, and not merely apparent. And so on with other sets of experiments. The inference which I have drawn is as follows: I. That the difference in the rate of corrosion between wrought iron and soft steel is rarely enough to be of great moment except, perhaps, in marine boilers. 2. That the ratio of the corrosion of given soft steel to that of given wrought iron may vary greatly with the conditions ~ of exposure. _ Of the apparent discrepancies between the results not only of different observers, but even of the same observers, I sug- gest two chief causes. I. The quasi-accidental variations, individual peculiarities, ete. : - 2, That the susceptibility to corrosion of soft steel, taken as a whole, does differ somewhat from that of wrought iron, taken as a whole; but that this difference is of such a nature that wrought iron asaclass corrodes on an average faster ~ than soft steel under certain conditions, but slower than soft - steel under others. -. But, we may ask, What are the differences in composi- tion or constitution between wrougbt iron and soft steel, which are capable of producing a difference in susceptibility to oxidation, which diffzrence itself is liable to change not only in intensity but even in sign? “*Abstract of paper read at the International Congress on ‘‘Methods of Testing the Materials of Construction.” : . Apart from the fact that wrought iron usually contains less manganese but more phosphorus than soft steel, we have two important differences; wrought iron contains a considerable quantity of ‘‘conder’’ or ‘‘scale’’ in flakes or sheets mechanically intermixed with the pure iron or fer- rite; soft steel, while lacking this, has usually considerable more carbon than wrought iron. This carbon exists in the form of the definite carbide, Fe 3 C, called cementite, of which there are 15 parts by weight for every part of carbon present; so that for every 0.10 per cent. of carbon there is 1.5 per cent. of cementite. This cementite lies in microscopic flakes. It is, indeed, present in both wrought iron and soft steel, but the latter has usually so much more cementite than wrought iron has, that the excess of its cementite is of about the same order of importance as the excess of the flakes or “cinder” or ‘‘scale’’ in the wrought iron. Bach of these substances, cinder and cementite, should have a two-fold influence. First, as each resists oxidation powerfully, each should, like so much paint, mechanically protect the particles of the pure iron or ferrite underlying it; second, each by difference of potential should retard or hasten the corrosion of the iron, as the case may be. Let us distinctly recognize this two-fold influence of these two sub- stances, the cinder of wrought iron, and the cementite pres- ent in relative excess in soft steel; first, mechanically pro- tective; second, by difference of potential, perhaps hasten- ing, perhaps retarding, the oxidation of the underlying metallic iron. It is possible that’ this line of thought is new. The resultant of these two influences should vary with the nature of attacking medium, whether this be fresh water, sea water, acid or alkaline liquor; and it should also vary with the progress of the corrosion. When a piece of wrought iron or steel is first exposed to oxidation, it is only what we may call the outcropping edges of the sheets of cinder or of cementite which mechanically protect the underlying pure iron from oxidation. Those parts of the pure iron which lie originally at the surface, without overlying sheets of eementite or cinder, receive no mechanical protection. But as the oxidation proceeds and these outcropping parts of the pure iron are gradually dis- solved away, more and more of the cinder or cementite be- comes exposed and thereby prevents the air or water from reaching and attacking the underlying pure iron or ferrite. Thus, in short, the mechanical protection of the flakes both of the cinder of wrought iron and of the cementite of soft steel should increase as oxidation proceeds; but the pro- tection of the cinder need not increase in the same ratio as that of the cementite. It might well be that, since the cin- der is distributed in the wrought iron in a manner very dif- ferent from that of the cementite in soft steel, with the pro- gress of oxidation and with the gradual removal of the out” cropping pure iron, the mechanical protection of the cinder of wrought iron should increase much more than that of the cementite of soft steel. Hence, it is quite possible that though wrought iron and soft steel should corrode at the same rate initially, yet later (the oxidation of the wrought iron being retarded by the increased protection of its cinder more than the oxidation of the steel is retarded), the wrought iron should oxidize much less than the steel. Knowing that there was a widespread belief that wrought iron oxidixes less than soft steel, and yet having before me the results of such extensive direct experiments which indi- cate that it does not, 1t occurred to me that the discrepancy might be explained in some such way asI have here out- lined; for our direct experiments usually last a relatively short while, and represent rather the initial rate of oxidation than the latter rate; whereas, the opinions of industrial users of wrought iron and steel based on the results of indus- trial use, would represent longer trials, usually carried on to destruction. Fortunately data for testing this hypothsis were at hand; for in my own experiments and in another very extensive series, the oxidation of soft steel and of wrought iron for each of two successive long periods was given. Comparing these, I do not find that the oxidation of soft steel acceler- ates relatively to that of wrought iron as the period of ex- posure continues. Therefore, this reason for questioning the results of our direct experiments is weakened. But in view of it, all of my plates are still under exposure, and I hope to reweigh and report on them again after a further period of several years. As to the influence of difference of potential of the cinder of wrought iron and the cementite of soft steel, I have car- ried out a long series of direct experiments with various It would carry us too far even to outline the resul liquors. of these here. ; The following table sums up the results of my own exper iments: RELATIVE CORROSION OF SOFT STEEL, WROUGHT IRON AND NICKE STEEL, TAKING WROUGHT IRON AS A STANDARD. ae Sea. Fresh. ’ Aver. Water. Water. Weather. a Wrought iron..........---- 100 100 100 100 Soft steele ose iviese ee vee aes II4 94 I03 103 3 per cent. nickel steel..... 83 80 67 7 26 per cent. nickel steel.... 32 32 30 31 Nickel steel, both of 3 and 26 per cent. of nickel corroded under all conditions less than either wrought iron or steel, as was to be expected. The difference, however, was much less than might have been hoped. Ona general average the — 3 per cent. nickel steel corroded 77 per cent. as fast as the wrought iron, and the 26 per cent. nickel steel about one- third as fast as the wrought iron. The superiority of the 3 - per cent. nickel steel in this respect, thought decided, is hardly enough to weigh heavily in determining its produc- tion. The 26 per cent. nickel steel, while it certainly has an enormous advantage over common soft steel and wrought iron as regards corrosion, yet probably is at a great disad- vantage in this respect when compared with some of the copper alloys with which it will have to compete. We can- not call it a non-corroding metal under common conditions, it is simply a slowly corroding one. —————________Q@orn22oe TIDAL WAVES. ' What of the tidal wave, that mysterious indispensable swelling of the waves that, following the “puli’’ of the moon, rolls round this globe of ours twice in each 24 hours, stemming the outflow of mighty rivers, penetrating far in- land wherever access is available, and doing within its short lease of life an amount of beneficent work freely that would beggar the wealthiest monarchy of the world to undertake if it must needs be paid for? Mysterious it may well be called, since, tho its passage from zone to zone be so swift, it is, like all other waves, but an undulatory movement of that portion of the sea momentarily influenced by the suasion of the planet—not, as is vulgarly supposed, the same mass of water vehemently carried onward for thousands of miles. To meet a tidal wave at sea is in some parts of the world agrim and unforgettable experience. Floating upon the shining blue plain, with an indolent swelling of the surface just giving a cozy roll to your ship now and then, you sud- denly see in the distance a ridge, a knoll of water that ad- vances vast, silent, menacing. Nearer and nearer it comes, rearing its apparently endless curve higher and higher. There is no place to flee from before its face. Neither.is there much suspense, for its pace is swift altho it appears so deliberate from the illimitable grandeur of itsextent. It is upon the ship. She behaves in accordance with the way she has been caught, and her innate peculiarities. In any =: case, whatever her bulk, she is hurled forward, upward, backward, downward, as if never again could she regainan even keel, while her crew cling desperately to whatever holding place they may have reached.: Some will have it that these marvelous upliftings of the sea bosom are not tidal waves at all—that they do not be- long to that normal ebb and flow of the ocean that owns the sway of the moon. If so they would be met with more fre- quently than they are at sea, and far more disasters would be placed to their account. This contention seems reason- able because it is well known that lonely islets such as St. Helena, Tristan d’Acunha and Ascension are visited at irregular intervals by a succession of appalling waves (roll- ers) that deal havoc among the smaller shipping and look — as if they would overwhelm the land. The suggestion is that these stupendous waves are due to cosmic disturbance, to submarine earthquakes upheaving the ocean bed and , causing so vast a displacement of the ocean that its undul- ations extend for several thousands of miles.—Londcn Spec- tator. : : rr oo i NAVAL expansion is the order of the day. A study of the budgets of the various naval powers, the building programs as outlined therein, and the constantly increasing amounts devoted to new construction, all serve to indicate the seri- ous attention given to the subject of naval increase. England, as usual, leads with the lagest sum for the sup- port and increase of her navy. But large as is this total, it is generally felt that the admiralty program is inadequate, and the press of that country is actively urging a further increase.