i6o PRESERVATION OE METALS USED IN MARINE CONSTRUCTION. 



are the best. Even for decorative purposes this is not true, because 

 a proper paint properly appHed will generally last at least three times 

 as long as an improper one at half the price. Judging from the amount 

 of surface to be covered, the conditions of its service, the number of men to 

 do the work, and the other work they have to do, the best paint, properly 

 applied, is none too good and should be obtained at any cost. The writer 

 once put a coat of white enamel paint on the above-water sides of a gunboat 

 in service on the Yangstze-Kiang River which lasted without retouching for 

 over one year. It looked well all the while although washed daily with 

 muddy river water. 



As active corrosion cannot take place on dry metals it may often be 

 better not to remove a good film of paint that has been put on over dry dust, 

 and through which no signs of active corrosion are visible, than to spoil the 

 paint for the purpose of removing dry and therefore harmless rust unless it is 

 perfectly sure that a properly dried paint film can again be obtained over 

 perfectly dry metal. The writer has on several occasions done more harm 

 than good by removing good dry paint films previously put on over dry rust 

 because he could not get the surfaces dry and a proper film of good paint to 

 stick to them. 



The metals used in machinery boilers and their accessories and piping 

 are many such as — 



Cast iron for cylinders and engine housings. 



Steel for steam pipes, boilers, shafting, tanks, evaporators, condensers, 

 feed pipes and general piping. 



Composition for water boilers of pumps, water pipes, valve fittings, 

 boiler fittings, condenser tubes and in other places. 



Copper for small piping and in other places. 



Monel metal for valve fittings, pump liners, pump rods and such other 

 places. 



Cast steel for superheated steam valves, slip-joint castings, etc. 



Lead as a lining for iron or steel pipes. 



Other metals are used but the above are the principal ones. The same 

 observations apply to these metals that can be painted as previously stated 

 for hull materials. 



Oil films are moisture-proof when applied to dry metals, therefore there 

 is very little if any corrosion taking place about an engine when it is in use. 

 Paint around the usual main engines and their framing is unnecessary unless 

 the engine is to be laid up for a long period, and, if used, is for the purpose 

 of decoration only. The external sides of pipes, feed heaters, condensers, 

 boilers, evaporators and tanks can be protected by proper paints. The 



