Cleaning should also be studied bo develop improvements in both methods 

 and materials and to detei'mine if overall savin-'s ai-e possible. This is 

 important because cleaning is expensive at best, and it is uneconomic to 

 insist on doing something just because it has been standard practice in 

 the past. .'hile vie are on this subject of cleaning, it must not be for- 

 gotten that it is always present and for a much longer time during the 

 usage stages of our structures and it is at that time that it really 

 presents the biggest problem. This for the added reasons that inaccessi- 

 bility and a deteriorated condition nov/ present further complications, 

 i'iany methods of cleaning which are entirely feasible on a nevv and rela- 

 tively clean sti'ucture are totally inadequate when applied to a structure 

 virhich is covered with varying thickness of rust and almost every known 

 forni of tuberculation and fouling and rdth deep pits due to corrosion or 

 incorrect field welding practice. .'ben cleaning under such conditions is 

 considered, the uncertainties thereof and also the uncertainties of good 

 results from the later application of protective coatings xilll be easily 

 realised. 



Before considering coatings or treatments in lieu thereof, the question 

 of pre-coating treatments arises j that is, whether or not an inhibiting 

 solution such as sodium dichromate and phosphoric acid should be used. 

 This is standard practice in pickling operations and some authorities 

 insist that such a treatment should be used in any event. It has been 

 used on our ?,'ork sometimes by mistake but without any distinct results 

 one way or another so far as is knov/n. 



The matter of protective coatings for marine structures is one of the 

 most confusing and complicated subjects vre have to face. In fact, this 

 is a subject on whicli one never gets a completely satisfactory answer at 

 any time and the reacon for this is that basic conditions are never the 

 same on any two jobs. 'hen this is considered along './ith the climatic 

 conditions referred to previously and vith the factor of personalities, 

 such coKibinations of conditions occur that almost anything can happen 

 at any time and frequently it does. In this connection it is continu- 

 ously surprising that condition combinations which seem to clearly indi- 

 cate a certain result vflll suddenly turn up something quite different. 



Because of this it is not proposed to try ;:nd describe in too much detail 

 about coatings except to say that BuI3ocks has tested literally thousands 

 of them and unfortunately a great proportion of them have not done what 

 was claimed for them. This accounts for a previous reference to over- 

 enthusiastic salesmen or scientists and the dangers which might flow from 

 too close an adlierence at times to their recommendations. On the other 

 hand, all these trials and experments have resulted in some really good 

 coatings which meet requirements to an extent vvhich seems reasonable. 

 Full information on coatings used over the years is available to anyone 

 interested. Search is still being made for the "end of all trouble" 

 coatings, hov/ever, and the study and help oi the delegates here are 

 still needed. 



D- 5 



