1842.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



199 



CORROSION' OF IRON IN STEA.M BOILERS AND STOVHE PIPES. 

 fFrom the FrmMin Journal ) 



The Cmnmittee on Science and the Arts, constituted by the Franklin Institute 

 vf the State of Pennsylvania, for the promotion of the Mecltanic Arts, to 

 whom was referred for examination the Corrosion of Iron in Steam Boilers 

 and Stove Pipes, tvhere Anthracite is employed as fuel, Report: — 



That they have gathered such information as lay in their power from those 

 who have witnessed the corrosive action, and combined it with their own 

 observations. 

 > It appears that stove-pipes are frequently corroded in the course of a year 

 or two, where they are not taken down or cleansed subsequent to their em- 

 ployment through the winter season. An instance is known in which 40 ft. 

 of pipe were corroded and rendered a perfect colander in the course of two 

 Tears. Nor docs it appear always as a necessary condition that the place 

 should be damp, although this is the case in a majority of instances, for in 

 the corrosion just noticed, the proprietor stated that the stove was very dry. 

 The corrosion rarely happens in an upright pipe, but usually in one lying 

 horizontally, for where such corrosion had already commenced it was said, in 

 one instance, to have been obviated by giving the pipe a slight inclination. 

 >\'here it takes place in an upright pipe, it may arise from the flowing down 

 of corroding matter from a horizontal layer of the same. 



The same kind of corrosion is observable in steam boilers in which anthra- 

 cite is employed as fuel, and not in those in which bituminous coal is used. 

 That it does not arise from the intensity of the heat is shown from the fact, 

 that it is greatest in the boiler-flues which lie horizontally at a distance from 

 the fire, k corrosion is sometimes observed near the top of the smoke pipe 

 in steamboats, but this may be attributed to the alternate action of heat, 

 cold, air, and moisture. 



It would appear then, that the corrosion is caused either by the vapours 

 aHsing from the combustion of anthracite, or from matter carried up mechan- 

 ically by the draft; or from both combined. That it does not proceed from 

 incondensable gaseous matter is proved by the occurrence of the corrosion 

 only when a stove-pipe is no longer exposed to these vapours during the 

 summer season, or where a boiler is cooled from intermitted fires. It does 

 not arise from matter carried up mechanically, for this could only be ashes, 

 and we know that the ashes of anthracite are of a dry nature ; and without 

 moisture, chemical action, or the corrosion, could not occur. It must, there- 

 fore, be produced from condensable vapours. 



On examining the interior of a stove-pipe lying horizontally, whether 

 corroded or not, we find a loose ashy deposit of a greyish brown colour ; 

 and where corrosion has taken place, the greater part is condensed into a 

 solid mass, showing that it had absorbed water. Upon fracturing the solid 

 material, small white crystals appear under the microscope, which are gene- 

 rally too imperfect to admit of recognising their form. By subliming the 

 mass, a little empyreumatic oil and water are formed, but the greater part 

 subUmed is an ammoniacal'Salt. Upon testing a solution of the ashes, it 

 shows a large content of muriate and sulphate of ammonia, the former evi- 

 dently in much greater quantity than the sulphate. After complete sublima- 

 tion at a red heat, the ashy matter remaining appears to be nearly pure 

 charcoal or lamp black, with a mere trace of coal ashes. From the qualitative 

 tests made, it would appear that the ammoniacal salts constitute at least 

 three-fourths of the whole mass. A mere trace of iron was detected. 



From this content of saline matter, as well as from its nature, we are at 

 no loss to account for the corrosion of iron where the air and moisture add 

 their conjoint action ; but it may be doubted whether the ashy matter has 

 the power of absorbing moisture from an atmosphere of ordinary dryness, 

 for in dry situations, it appears that there is usually no corrosion, and in the 

 case noticed at the commencement of the report, it may be doubted whether 

 the stove was dry. 



How to obviate the corrosive action is a more difficult point to determine, 

 unless the very, simple process be resorted to of cleaning out stove-pipes 

 every spring, and hoiler-flues every few weeks. If the stove-pipes are required 

 to remain standing with the sediment in them, then a previous internal coat- 

 ing of white lead, litharge, or red lead might probably answer the best 

 purpose, since it would result in the production of chloride and sulphate of 

 lead, while the ammonia would be driven off. The thin coating of these 

 salts of lead might then prevent the contact and farther action of the ashy 

 deposit. Experiments made at the U. S. Mint during the winter of 40-41, 

 seem to show that a coating of lime on the interior of a pipe prevents cor- 

 rosion, and it is said that a few stove manufacturers in this city are acquainted 

 with the fact. The committee, however, in the face of these facts, are rather 

 inclined to believe that the oxide of lead will prove more efficient, since the 

 sulphate of lead is a wholly inert salt, and the chloride nearly insoluble, 

 while the sulphate of lime is somewhat soluble, and the chloride of calcium 

 very soluble, and therefore likely to produce corrosive action eventually. 

 Still the operation of whitewashing is tbe simplest mode of obviating cor- 

 rosion, and may be repeated at intervals. 



The content of chlorine to such an extent as is developed by the above 

 chemical examination, is interesting in a geological point of view, since it 

 has not hitherto been found in chemical examinations of anthracite. Prof. 

 H. D. Rogers, in 1836, point«d out the fact, that where heaps of refuse 



matter were burned near the coal mines, ammoniacal salts, and among them 

 muriate of ammonia, are sublimed, and may be found among the ashes. Now 

 we know that saline waters are obtained from the coal measures in the west- 

 ern district of Peiinsylvania, and, moreover, it is the prevailing opinion 

 among geologists that the coal series are marine deposits ; we can, there- 

 fore, explain the origin of the muriate of ammonia in the ashy deposit 

 arising from the combustion of anthracite, by attributing the chlorine to the 

 presence of a trace of chloride of sodium (common salt) in the coal or its 

 accompanying slate, or possibly in both. It is unnecessary to allude to the 

 formation of ammonia, since it is a universal product to a greater or less 

 extent of the dry distillation or combustion of every kind of coal. 



This ammoniacal deposit is interesting in an economical point of view, 

 since it accumulates in considerable quantity in a single season, and may be 

 collected with facility. In one instance at least, ten pounds were removed 

 from about eight to ten feet of pipe, which was the produce af three or four 

 years, and hence, we may estimate the large amount that might be obtained 

 from many hundred pipes in Philadelphia every season. It may be employed 

 either for the manufacture of sal ammoniac by a very simple process of sub- 

 limation with a small quantity of a salt of lime, or it may be directly applied 

 in powder or in solution to garden soils. The influence of ammoniacal salts 

 in promoting luxuriant vegetation has long been known, but the admirable 

 work of Prof. Liebig on Agricultural Chemistry has more completely de- 

 veloped their influence and importance. The material before us will unques- 

 tionably prove of great value to the gardener and florist, if properly applied 

 to the soil ; but it must not be forgotten that it is very rich in ammonia, and 

 should therefore be employed sparingly. 



February 10, 1842. 



By order of the Committee, 



William Hamilton, Actuary. 



PROCEEDINGS or SCZESTTIFIC SOCIETIES. 



• 



INSTITUTION OF CUIL ENGINEERS. 

 March 1. — William Cdbiit, V.P., in the Chair. 



" Holhom HiU, and the Plans for its Improvement." By John Turner. 



This communication chiefly consists of an examination of the various plans 

 which have been suggested for diminishing the acclivity of that crowded 

 thoroughfare. An idea of its thronged state is given from Mr. Xttiishaw's 

 evidence before a Committee upon Metropolitan Improvements, in May, 

 1838, wherein he assumes the fair average annual amount of traffic between 

 Fetter Lane and the Old Bailey at " 20,000,000 pedestrians, 871,640 eques- 

 trians, 157,752 hackney coaches, 372,470 carts and wagons, 78,876 stages, 

 82,258 carriages, 135,842 omnibuses, 460,110 chaises and taxed carts, and 

 354,942 cabs." The necessity for ameliorating this great thoroughfare has 

 been generally acknowledged, and great changes have been made in the 

 locality since the rivulet called the " Old Bourne " took its course down the 

 hill into the Fleet river, which at that time had wharfs on either side for 

 landing goods from the barges, which came up as far as llolborn Bridge. 

 About the year 1733 the arching over of the channel of the Fleet was com- 

 menced, and subsequently was extended to the Thames, forming at present 

 one of the main sewers, having its outlet at Blackfriars Bridge. On arching 

 over the Fleet the ground at the bottom of the hill was raised as much as 

 possible ; indeed all that can be done by filling up (having reference to the 

 surrounding levels), would appear to have been done at various intervals. 



The oldest plan mentioned by Mr. Turner is that by Mr. T. F. Taylor, in 

 1828. He proposed to divide the hill at the corner of Hatton Garden into 

 three parts, and to continue the same up Skinner Street nearly to the Sara- 

 cen's Head Inn ; between these points an iron suspension bridge, with a level 

 roadway, was to be erected wide enough to admit of two carriages abreast, 

 leaving the footpaths and nearly all the houses undisturbed. Tlie estimate 

 for this plau was about £23,000. 



In 1833 Mr. Turner proposed to construct a bridge or viaduct, upon arches, 

 along the south side of Holborn Hill and Skinner Street, from Thavies Inn 

 to Sea-coal Lane. The arches would have been available for warehouses 

 upon the level of that half of the street which preserved its original position. 

 On this plan it would have been necessary to take down all the houses on 

 the south side from Shoe Lane to Farringdon Street ; the others being 

 modern, might have been raised. This plan was subsequently modified, and 

 the width of the street increased to 70 feet, giving the viaduct 35 in breadth. 



Mr. Moselev's proposition in 1833 was to fill up the valley to the height 

 of 12 feet at llolborn Bridge, altering some of the houses at the bottom. In 

 1840 he further proposed to take 18 inches off the brow of llolborn Hill and 

 12 inches oflT Skinner Street, which, with raising the bottom, would bring 

 the gradient of the acclivity to about 1 in 35. 



Some interesting tables are given of the rates of acclivities of some of the 

 principal thoroughfares in Loudon. 



