Item No .

1 Stream of compressed humid air

0.0480 0.0020 24

2 Water with 500 mg / l Н2S

3 Sea medium ( waterline zone with high air inflow in presence of water or water film with a high content of dissolved salts )

4 Cold and hot water supply systems

5.21 0.0565 92

0.30 0.005 60

0.923 0.0022 42

5 Process water at oil refineries and coke plants

( 200 ) ( 40 ) 5

Table 2 . Corrosion resistance of diffusion zinc coatings in various media

To confirm the high corrosion resistance of diffusion zinc coatings in comparison with other types of zinc coatings , the results of corrosion tests of various types of zinc coatings under harsh operating conditions ( pipelines on tankers and other sea vessels , hot-water supply pipes , etc ., tubular equipment of coke production plants ) are given hereinafter . ( Table 2 ).

The results of accelerated corrosion tests of steel samples with zinc coatings applied by various methods in media containing corrosive components ( the conditions simulating the effect of a mildly corrosive industrial atmosphere ) are presented in Fig . 3 .

Comparison of the main properties and results of special corrosion tests of various zinc coatings shows that diffusion zinc coatings in the hardest operating conditions are the most effective for protecting surface of steel pipes and other metal products ( Table 3 ).

The test results ( Table 3 ) show that the corrosion rate of the diffusion zinc coating in the moving aqueous medium of the hot water supply systems was significantly less than that of the hot-dip galvanizing coating and gradually decreased in time .

Fig . 3 . Kinetics of corrosion of zinc coatings in conditions simulating mildly corrosive industrial atmosphere with SO2 ( GOST 26294-84 ) ( 1 month of testing corresponds to ~ 1.2 years of full-scale testing )

22 TUBE NEWS June 2018