Corrosion behavior of steel under the conditions at the Krasnoyarsk hydroelectric plant

Conclusions

• 1. The corrosion rates of steel in water during short-term tests under conditions prevailing at the Krasnoyarsk hydroelectric plant, and also in all river basins of the middle latitudes in the northern hemisphere vary considerably during the course of the year. They diminish markedly in the winter, reaching 10–20% of the corrosion rates in seawater, and increase vigorously in the summer, attaining 300% of the corrosion rates in that same medium.

• 2. In the Enisei, as in the other rivers, the corrosion rate of steel in the zone of periodic wetting under the surface of the water is, in contrast to marine conditions, close to the corrisoon rate in the air, while under marine conditions, vigorous corrosion is observed to be many times greater in this zone.

• 3. Under Enisei River conditions, as in other rivers, the underwater zone is the most aggressive; this also distinguishes river from marine corrosion, where the rate in this zone is 4–5 times lower than that in the zone of periodic wetting, and is approximately equal to the rate in the air.

• 4. Long-term field studies conducted at the Krasnoyarsk hydroelectric plant indicate that under conditions prevailing here, the application of coatings to mechanical equipment and metal structures would probably be necessary not so much to protect them from corrosion, as to provide the required ornamental appearance.

• 5. Metallizing the surface of design components with aluminum to a thickness of not more than 50 μm can be recommended as a protective-decorative coating.

Use of cathodic protection is expedient for the underwater zone, where the corrosion rate (possibly due to the formation of vapors of differential aeration and the combined action of corrosion and erosion) may have a more significant effect on the designs than has been shown by the testing of specimens.