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GEraee EMRE Ee Ne pioneers 'of industrial progress. April, 1911 fuel. It might be mentioned that the directors of the above company have ~ distinguished themselves in the past as They were first in Russia to foresee the possibilities of oil to liquid fuel for steam engines, and first began stoking "TAE MaARING REVIEW steam boilers on their steamers with oil instead of coal or wood. Now they are taking a step forward in the direction of utilizing oil for navigation, which may be expected to meet with just as complete a success as their first step in that direction. Some Practical Experience with Corrosion of Metals By ENcINrer Rear-ApmiraL JoHN T. Corner, C. Bt i. SHOULD be pointed out at the outset that in this paper the writer purposes to limit himself to chiefly giving instances of corrosion which have come under his notice whilst ac- lively engaged as a marine engineer, and to detail some of the practical methods found to be efficacious in dealing with the same. Some of the causes. of corrosion of. metals on shipboard are so obscure, and the origin so difficult to trace, that no satisfactory explanation is so far forthcoming. On the other hand, cases have occurred in which the causes operating to produce the ef- fects are clearly recognized and easily dealt with. The writer has had no personal ex- perience of the trouble which took place through the corrosion of cop- per and its alloys in the old wooden ships, but that such corrosion did ex- ist is within the knowledge of most of those who have studied the record of such ships. Cases are mentioned of copper sheathing having become corroded in mysterious ways and at unexpected times, and there are re- ports of the heads of the nails having corroded entirely off, allowing the sheathing to become detached. There were doubtless at times trou- bles through corrosion in the bilge and other copper pipes of the old wooden steamships of war, but as a rule these appear to have -been of minor importance; and in many ships the chief anxiety the engineers had concerning the pipes was to keep them in a bright and burnished con- dition so as to pass the captain's weekly inspection, at which the array of copper piping in the bilges was often one of the show sights of the ship. With the introduction of iron for ship building purposes the conditions *Institute of Metals. +Late chief engineer of yard. Portsmouth dock were different, for it was soon found necessary to insulate as well as pro- 'tect the copper pipes in or near the bilges--not, however, for their own welfare so much as for the sake of the adjacent plates and angles, which, when not so treated, were found to be adversely affected by contact, owing - to the galvanic action set up between the metal pipes and the iron plating by the bilge water. The Introduction of Iron. There are many instances in which very considerable trouble was caused. Among them may be mentioned the case cf the troopship Megaera, which vessel had to be beached at St. Paul's Island, about 1869, to prevent her sinking. It came out in the subse- quent inquiry that among other de- fects in this ship, there was a serious one due to a copper strainer fitted to a bilge suction pipe in a remote . part of the ship. The action set up by it was sufficient to: eat right through the plates and so' admit water to such an extent that the ship had to be run ashore to save her crew. As far as can be ascertained, the pipes themselves in iron ships were no more affected than those in wood- en ships, probably not so much; and it was not until at or about the time of a great change in the internal econ- omy of men-at-war that serious and persistent trouble through the cor- rosion of copper pipes began to be manifest and felt. This. change was the introduction of the electric light on shipboard. Corrosion of Copper Pipes. The writer's first experience of the insidious corrosion of copper pipes oc- curred in a ship which had recently been fitted with an electrical installa- tion for working searchlights. Dur- ing a commission of over three years, there were, as far as can be remem- 141 bered, only two pipes which seriously suffered from corrosion; both were water pipes, and both were eaten right through in small holes which had the appearance of having been punched, and it is noteworthy that each of these pipes was in the immediate vi- cinity of an electric lead to a search- light--the one forward and the other aft. The whole business was after all but a minor affair, and consequently very little notice was taken of it; it was only years afterwards when trying to assign a cause for similar trouble in various other ships that the previous experience was fecalled to throw light on an obscure ques- tion. There is no doubt whatever that the time of the introduction of the electric light in naval ships synchron- ized with a considerable increase in the corrosion of the copper and metal pipes and fittings; and as the parts affected were chiefly water fittings, the increased steam pressures which came at or near this period, and which might have been suspected as one of the causes, can be now quite absolved from any share or part of the trouble. Sometimes pipes would be found eaten nearly, and in some quite, through in a very short period; more- over, the replaced parts often became similarly affected even when different brands or qualities of copper or brass were used. Sometimes the pipes were eaten in holes having sharp, clean-cut: edges, as though punched; sometimes parts were pitted and honeycombed over a considerable area of surface; while in other examples the metal was nibbled out in such a way as almost to suggest the presence of rodents or microbes. Speculation "as to Source. As regards the source of this trou- ble, some engineers for the reasons above stated were inclined to attribute 'it to electrical action due to the leak- age from the mains, which was often so great as tc allow electricity to per- meate the whole ship. It must be admitted now that some of the earlier electrical installations on shipboard were a long way from perfect, inas- much as leakage in some cases was sufficient to turn the ships into stor- age batteries, Others attributed these defects in the copper pipes to induced currents set up in different parts of the ship by the currents in the elec- trical mains. But nothing definite could be proved, and those then deal- ing with the electrical plant disclaimed all responsibility for the trouble, and, in fact, sometimes expressing the