Use of metallic coatings for corrosion protection of mechanical equipment at the 22nd CPSU Congress Volga Hydroelectric Plant

At the Twenty-Second CPSU Congress Volga hydroelectric plant, for the first time in Soviet practice use was made on a wide industrial scale of corrosion protection of the spillway gate metal structures by means of metallized zinc--aluminum coatings. This type of protection was selected on the basis of das from previous investigations carried out at this plant [i], which had revealed high resistance of aluminum coatings. As a result of the investigations, it had been proposed to protect with aluminum coatings only the zone of atmospheric corrosion and periodic wetting, whereas use of electrochemical protection had been recommended for the underwater zone [2]. Metallization was used for 22 gates altogether. The coating had the following constructional characteristics. On the metal surface to be protected, a 50-Bm-thick zinc underlay was applied by the ~as-flame method and this underlay was then covered with a 150-~m-thick aluminum layer applied by the same method.This work was started in 1967, when a 22 x 13-m mate with a total area of I000 m 2 was protected.During 1971-1972 four gates were. protected --two per year. During 1973-1976 three gates per year were protected.In 1977 two gates were protected, and during 1978-1979 one gate was protected per year.In 1979 a detailed inspection of the state of all the metallized gates operating at the Vol~a plant was carried out. All the surfaces in contact with the atmosphere at the nonpressure side of the gates and the upper part of the pressure side were in good condition, andd they did not exhibit traces or patches of steel corrosion products (Fig. I). Wear of the coating is observed to a certain extent only at the top of the gate on the external horizontal surface of the beam, in places of permanent accumulation of atmospheric moisture. Evidently, in new g&tes this surface should be made inclined to ensure full flow of rain water through a drain at the lower edge.Of great interest was the inspection of a gate which has operated under severe conditions of action of water, ice, mechanical impact from ice and floating logs, and low winter and high summer temperatures for 12 years. This inspection, carried out by drying the coating and measuring its parameters in detail, showed that, despite the absence of the previously contemplated cathodic protection on the lower underwater portion of the gate and the insufficient thickness of the applied coating, the protective layer had been preserved in all zones of contact with the water. On the surface above the upper water line, corresponding to the flood reservoir level, the coating thickness was practically unchanged and remained equal to the original 120 Bm. In this zone the gate did not exhibit any traces of corrosion or mechanical damage. The aluminum coating potential was equal to-0.44 V with respect to the comparison copper sulfate electrode (cse). Below the upper water line, in the zone of variable level, the aluminum coating was lacking, probably because of incorrect application of the coating. Aluminum corrosion products o...

Corrosion protection of spillway gates at the Twenty-Second CPSU Congress Volga hydroelectric plant

Masol'd¹,

Nemkovskii²,

Trifel³

1980

Corrosion and cavitation protection of steel hydroelectric station structures and equipment

1974

Steel structures and equipment of hydroelectric stations, constantly or periodically operating in water, at places with a highhumidity, and in the open air under atmospheric effects -hydraulic turbines, penstocks, surge tanks, gates and emergency gates, trash racks, auxiliary equipment with pipelines and fittings, etc. -constitute a considerable part of the productive resources of hydropower engineering. The total weight of steel in structures at hydroelectric stations amounts to about 1.5 million tons, including more than 0.3 million tons in turbines. Protection of steel structures against damage by corrosion and cavitation is an important economic problem.An increase in the service life of steel structures is an important factor in the economy of maintenance and operating expenses at hydroelectric stations, not oaly as a consequence of the direct reduction in steel consumption but also as a consequence of the reduction in labor costs, since work on the protection and restoration of structures subjected to corrosion and cavitation number among the heaviest and most labor-consuming repair operations performed at hydroelectric stations.The following methods are used for protecting steel structures against corrosion: use of resistant metals and alloys, isolation of the surfaces being protected from the external corrosive environment (organic. metallized, and other coatings), and electrochemical protection.

Problems of increasing the operating effectiveness of hydroelectric stations

1975

are holding a scientific-technical conference devoted to problems of increasing the operating effectiveness of hydroelectric stations. At the conference there is to be an exchange of experience and mutual information on improving the operation of hydroelectric stations, developing recommendations on the further increase of the effectiveness of water resources use, reliability of hydropower equipment and hydraulic structures, effectiveness of using hydroelectric stations in power systems, introducing progressive methods and means of operation and maintenance, increasing labor productivity, and decreasing operation costs. The high effectiveness of the hydroelectric station operation is characterized, for example, by the fact that during the years of the Ninth Five-Year Plan 250 million tons of reference fuel (i.e., fuel with a calorific value of 7000 cal/kg) was saved as a result of the output of hydroelectric stations; about 60-70 million man-hours of operating personnel labor are saved annually at hydroelectric stations. The development of hydropower resources simultaneously fosters the development of many branches of the national economy (irrigation, water supply, transport, fishery, etcJ. Taking into consideration the importance of the conference being held for the development of hydropower engineering and increasing the operating effectiveness of hydroelectric stations and pumped-storage plants, the editor of the journal "Gidrotekhnicheskoe Stroitel'stvo" is publ~hing in this issue a series of articles devoted to these problems and invites specialists to submit their articles and comments for the purpose of exchanging experience in the operation of hydroelectric stations.