Open AccessEffect of corrosivity on environment on the residual corrosion rate of steel in the specified range of protective potentials
Author(s) -
L.I. Nyrkova,
S.O. Osadchuk,
А. V. Klymenko
Publication year - 2020
Publication title -
naukovij vìsnik ìvano-frankìvsʹkogo nacìonalʹnogo tehnìčnogo unìversitetu nafti ì gazu
Language(s) - English
Resource type - Journals
eISSN - 2415-3524
pISSN - 1993-9965
DOI - 10.31471/1993-9965-2020-1(48)-7-15
Subject(s) - corrosion , carbon steel , cathodic protection , polarization (electrochemistry) , residual , materials science , aqueous solution , metallurgy , chemistry , electrochemistry , mathematics , electrode , algorithm
Studies’ results of the effect of environment’s corrosivity on residual corrosion of carbon steel in specified by DSTU 4219 range of protective potentials is presented. It is shown that this index depends on a number of factors – the polarization potential, the duration of the test and pH. It was demonstrated the decreasing of residual corrosion rate with increasing (in absolute value) of protection potential for environments with pH in the range from 5.6 to 9.6. It is shown that under the same protective potential for 8 hours in these environments, the residual corrosion rate of steel is different. At a minimum potential of -0.75 V in the environment with low acidic and strongly alkaline pH (5.6 and 9.6, respectively) the protective effect (i.e. a decrease of the corrosion rate to the values less than 0.01 mm/year) not achieved. The minimum values of corrosion rates, which are setting are 0,021 0,040 mm/year, and the conditions for the flying of local corrosion can create. In slightly alkaline environment (pH of 8.2) the protective effect achieved at the potential -0,72 V, and minimum protective potential the cathodic protection is effective. With the increase of the duration of investigations up to 1 month in all environments the protective effect achieved at the minimum protection potential, and under it increasing (in absolute value) decomposition of an aqueous solution, accompanied by hydrogen recovery. The rate of residual corrosion in solutions with different pH varies with time: through a short test time (near 8 hours) decreases nonlinearly with increasing the test time (up to 1 month) – a complex dependence on the potential with the minimum values in the area of alkaline pH is observed.