Promotion of drop‐by‐drop condensation of steam from seawater on a vertical copper tube

A limited number of tests were made of promoters, their method of application, corrosion resistance, etc. The best promoter found to date is tetrakis octadecyl thio silane (C 18 H 37 S) 4 Si which differs only in parafinic chain length from (C 12 H 25 S) 4 Si which was found to be one of the best promoters for drop‐by‐drop condensation by Blackman and Dewar ( 1, 2 ), Hampson ( 2, 3 ), and Osment ( 4, 5 ). These compounds are nontoxic. The C 18 compound appears to be superior to the C 12 compound in that it is less volatile, lower melting (∼34°C), and appears to impart superior oxidation resistance to copper when adsorbed on clean oxide‐free metal. Copper tubes can be rapidly cleaned in place by sulfur dioxide or hydrochloric acid in steam, or, if previously promoted by a thio silane, by treatment first with chlorine gas in steam. The thio silanes may be rapidly applied as a 1% solution in octanoic acid injected into the sea‐water feed. The acid acts as cleaner and poor promoter, allowing the good promoter molecules to contact the metal tube. The amounts of the best promoters required are in the parts per billion range.