The construction and materials of heat-exchangers should ensure their trouble-free exploitation over the entire service life and the retention of their efficiency factor. In the case of aggregates that are exploited in the atmosphere of a humid-tropical climate, the main factor that leads to the deterioration of exploitation characteristics is corrosion of the external surface of heat exchangers.The rate of atmospheric corrosion is determined by the corrosivity of the media [1], which, on the one hand, can lead to a thinning of the walls of the heat-transferring surface up to its perforation and, on the other hand, to a reduction in the heat-transfer efficiency due to the formation of dense corrosion products on the surface.At the Kudankulam nuclear power plant (India), aircooled heat exchangers intended for the removal of residual heat emission of a reactor in emergencies (e.g., the loss of all sources of electric power supply) are used as a system that should guarantee the passive safety of the reactor in such an emergency (passive heat removal system, PHRS).It is known that the main characteristic of a tropical climate is high temperature (20-35 ° C) combined with high air humidity for long periods of time [2,3]. The atmosphere in the region of the Kudankulam nuclear power station is characterized, apart from high temperature and air humidity, by a high content of corrosive agents such as chlorides (100 mg/(m 2 day)), sulfates (50 mg/(m 2 day)), sulfur dioxide (0.025 mg/m 3 ), ozone (190 µ g/m 3 ), etc.The most complex structural and technological features, from the point of view of corrosion protection, that wholly determine the service-life capacity are the heat-exchange coils of PHRSs (pipes 25 mm in diameter with walls 2.5 mm thick (steel 20) and ribs made of a ribbon 1 mm thick (steel 10)).The necessity of applying protective coatings (PCs) has been confirmed by the results of determining annual corrosion losses in a humid-tropical climate (corresponding to conditions of maintenance of PHRSs).The appearance of the templates after the tests shows intense corrosion of the surface of the coil elements; the average rate of corrosion of structural materials (steel 20) is, according to the results of metallographic investigations, about 95 µ m/year when there are such local defects as pits with a maximum depth of up to 90 µ m (without allowance for the loss of metal due to general corrosion) and crevice corrosion at sites where the ribs are welded to the pipes.The experimentally obtained values of the rate of general corrosion agree well with the calculation by the equation that is included into the modified standard ISO 9223 [4]; namely, K = 90 µ m/year at T = 25 ° C and Rh = 80%; K = 95.9 µ m/year at T = 28 ° Cand Rh = 80%; K = 99.9 µ m/year at T = 30 ° Cand Rh = 80%; K = 104.9 µ m/year at T = 25 ° Cand Rh = 85%; K = 111.3 µ m/year at T = 28 ° Cand Rh = 85%; and K = 116.6 µ m/year at T = 30 ° Cand Rh = 85%.These results, as might be expected, have unambiguously shown how necessary it is to protect the heatexc...

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