Bohn is currently investigating a new Dow-Corning material that is reported 

 to give protection equivalent to anodizing for aluminum coils. They feel 

 that they already have a good method of surface preparation in Alodine 

 1200, a chromate conversion coating qualified under MIL-SPECS C-5541B 

 and C-81706, They are prepared to do production coating in-house when 

 they find a suitable material. 



The Wilmington Coil Division of Singer Co, coats all small coils, in- 

 plant by dipping; they have experimented unsuccessfully with plastic and 

 pehnolic coatings that could be quoted as less expensive substitutes for 

 Heresite 



McQuay-Perfex has developed a vinyl chloride coating which has been 

 tested successfully in a coastal Florida location for performance com- 

 parison with Heresite„ Because of its toxicity, this coating is not used 

 for batch dipping of assembled coils. It is claimed to have potential 

 for pre-coating fin stock. 



IV, AVAILABLE COATING TECHNOLOGY 



In dealing with air conditioning equipment and its protection from 

 corrosion, consideration must be given to the extensive array of metal 

 finishing technology that has arisen in the manufacture of automotive, 

 ordnance, and aerospace equipment used by the military, including the 

 Navy and Marine Corps, A great deal of this technology, although to 

 some extent proprietary, is covered by military specifications. It may 

 be more applicable to coatings for heat exchangers than coatings used in 

 construction and maintenance of facilities, which is the area where CEL 

 has done the majority of its coating research. Thus, this investigation 

 included a review of industrial metal finishing practices summarized 

 by reference 10 and the industry guidebook of reference 11, For organic 

 finishes, reliable data on severe atmosphere performance of a number of 

 paint coatings is contained in references 12 through 14. Unfortunately, 

 comparable data is not available on inorganic metallic coatings and 

 chemical surface treatments for non-ferrous condenser coil materials, 

 What data does exist from industry experience is fragmentary and highly 

 subjective; documented results of exposure tests on which to base 

 engineering judgment would certainly be desirable. Cost data is more 

 readily available; costs for selected finishes are summarized by the 

 attached tabulation. 



Coatings of Interest 



Coatings of particular interest for further laboratory or field 

 testing include: 



Electroless Nickel, MIL-C-26074A -- This coating is ductile, 

 dense and impervious with good abrasion resistance. It can 

 be applied to both copper and aluminum, before or after fabri- 

 cation. Being chemically deposited, uniform coatings are 

 possible on irregular surfaces. Coatings as thin as 3/10 

 mil provide satisfactory protection. 



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