that is i/hat will be necessary to use since big heavy hard timbers 

 are harder to get all the time. Perhaps plastics can be made to serve 

 here, as they are doing elsewhere. 



Going on to our steel structures the big problem which is always present 

 is corrosion. This can come about because the structure is always sub- 

 merged or partially submerged in salt water as in the case of a steel 

 pile pier, floating dry dock, derrick, pontoons, barges, etc, and also 

 where the structure is not submerged but contains virater on the insidej 

 and do not minimize this second category either because sometimes it 

 is even almost more unbeatable than the other. An example is a structure 

 like a submarine escape training tank, such as the one at New London, 

 Connecticut. This is a steel tank structure 20' in diameter and 100' 

 high with an operating building on top and locks on the s ide at several 

 points and a section of a submarine built in at the bottom. To minimize 

 troubles here, fresh water is used as an operating medium but the local 

 river water is slightly brackish at times, contains hospital and factory 

 wastes, the inside tank surfaces must be white or some other light color 

 for maximum safety. The medical personnel insist that the T/ater be 

 heated, filtered and chlorinated and because a diving bell operates 

 therein with strong lights and telephones, there is, it seems, every 

 factor making for a difficult steel surface protection job, A great 

 many paint coatings ";/ere tried out in this tank before one was found 

 which would hold up for any reasonable length of time and this one costs 

 us about .,12.00 per gallon for the final cost. All the coatings studied 

 here have been catalogued and this information is available to interested 

 parties. 



It is pleasant to report, hov/ever, that all our steel protective coating 

 problems are not as tough as that one but even so, they are immensely 

 difficult to cope '/ith and are complicated by a factor mentioned previously 

 in this paper and that is by the great ran^e of climatic conditions en- 

 countered. By this is meant that a bituminous coating for instance, which 

 T/ould hold up fine in a hot climate like Uobile, Alabama, Tfould not do so 

 trell or might even fail comi-iletely if the same type structure on which i;^ 

 was used is built in or moved to the Arctic. In fact, this very condi- 

 tion has been experienced and must therefore be taken into consideration 

 at all times '..'hen steel structures ai'e built. 



This matter of corrosion starts with construction and in floating struc- 

 tures at I'-ast brings up the old argument of pickling versus mechanical 

 cleanin;^. In general, comnercial practice is followed and pickling not 

 used. But, on the other hand, a firm belief is held in a most thorough 

 cleanin''-; job including flame and mechaniccQ. cleaning, sand blastin:;, etc., 

 where required. For combat vessels, by comps, risen, pickling is standard 

 practice with a minimum of mechanical cleaning aiterv'^ards. Both methods 

 seem to provide us virith a '^ood long-life floating craft but it is desired 

 to knov/ vrhich system is the better. Since a lot of extra expense is invol- 

 ved in both systems, a rjresent day evaluation of the two methods is desir- 

 able and that T^roblem is presented here as one well worthy'- of some study. 



D - U 



