A Treatise On The Principles And Practice Of Dock Engineering

PRESERVATION OF IRON AND STEEL. 145 clear water and using a stiff scrubbing brush. The gain in weight of certain of the specimens represents the amount of deposit which could not be removed in this way. No further measures were taken to remove the deposit, becanse it was deeined desirable to maintain the normal conditions of corrosion. The last three specimens were kept continuously immersed in the water of an inner dock, which was free from contamination. Précautions were taken to prevent any contact between the various pieces, and all were well washed prior to each weighing.* TABLE XI. Nature of Specimen. Nett Area of Surface exposed Initial Weight. Weight at end of 1 Month. Weight at end of 3 Months. Weight at end of 6 Months. Weight at end Of 12 Months. Total Loss in 12 Months. Loss per sq. in. of exposed Surface. Sq. ins. Grains. Grains. Grains. Grains. Grains. Grains. Grains. Casting, plain, ,, galvanised, 37-12 19,473 19,499 19,526 19,510 19,457 16 •43 36-87 18,272 18,228 18,170 18,197 18,069 31,083 203 5'50 Wrought-iron bar, plain, 54-96 31,126 31,175 31,173 31,167 43 '78 ,, galvanised, 54-38 31,437 31,351 31,282 31,278 31,243 194 3'56 ,, turned, 58-35 31,172 31.187 31,185 31,143 30,988 184 3'15 Steel bar, plain, . 23-89 6,662 6,672 6,685 6,671 6,633 29 1 -21 Cast-iron plate, Wrought-iron plate, 77'5 16,979 16,976 16,965 16,943 16,972 7 •09 75-25 12,903 12,883 12,838 12,814 12,854 49 -65 Mild steel plate, . 75-25 13,519 13,503 13,483 13,453 13,406 113 1-50 It may be useful, as well as interesting, to insert here an analysis of the water of the Kiver Mersey, made by Mr. Charles C. Moore, F.I.C., in Sep- tember, 1897. The sample was taken about the time of high water, and its spécifie gravity was found to be 1-02254. The water contained the following salts in solution :— Sodium chloride, 22-35 grammes per litre. Sodium bromide, 0-32 Potassium chloride, .... 0-54 Magnesium chloride 2-78 „ ,, Magnesium sulphate, .... 1'785 ,, ,, Calcium sulphate, 1-9 Calcium carbonate, .... 0-04 Total dissolved salts, 29-715 Préservation of Iron and Steel.—The two principal measures adopted for preventing corrosion are painting and galvanising. Painting is an operation which should be repeated, at least, once in three years under normal conditions, and oftener in exposed situations. * In regard to this last operation, the author desires to acknowledge the kind assist- ance he received from Messrs. II. Pooley & Son, Ltd.