I. N. Ulyanov Chuvash State University (Cheboksary, Russia):

I. E. Illarionov, Dr. Eng., Prof., Head of the Chair of material science and metallurgical processes, e-mail: tmilp@rambler.ru
Sh. V. Sadetdinov, Dr. Chem., Prof., Chair of material science and metallurgical processes

The process of corrosion of 08kp steel used for the manufacture of VAZ car bodies in an environment that simulates the road conditions of car operation has been considered. Studies of road surface contamination samples of the M7 “Moscow-Ufa” motorway have established that the main components of pollution are chloride Cl^–, ammonium NH₄⁺, SO sulfates and NO nitrates ions. To determine the corrosivity of the road surface pollution, studies have been conducted on the influence of the environment simulating road conditions (ESRC) on the 08kp steel corrosion processes. Corrosion tests were carried out by experimental determining the mass loss of the samples in the test media. By measuring the stationary potentials of 08kp steel in the studied media with the help of a high-resistance voltmeter of the P-5848 potentiostat, information was obtained about the passivating properties of carbamide borate compounds depending on the concentration. It was revealed that potassium urea monoborate (PUMB) with concentration of 5 g/l possesses the best inhibiting action. Electrochemical measurements using the P-5848 potentiostat in the potentiodynamic polarization mode showed that the steel dissolves rapidly in the ESRC solution. In the presence of carbamideborates with the concentration of 5 g/l, the potentials of metal dissolution are shifted in a positive direction relative to E_cor in the background electrolyte. In this case, inhibitory additives lithium tetrahydrate carbamide dimonoborate (LTCDMB), sodium carbamide dimonoborate dihydrate (SCDMBD) and PUMB mainly slow down the anodic process. By fatigue and corrosion-fatigue tests of 08kp steel in the ESRC solution with and without PUMB additive, it was established that the total loss of cyclic strength of the studied steel in ESRC based on the N = 2∙10⁶ cycles test is 11.2 MPa. Of these, 74.1% accounted for only corrosion damage and 25.9% – for the corrosion-mechanical one. The addition of PUMB in the amount of 5 g / l to the ESRC solution increases the cyclic strength of steel and equally reduces the destructive effect of purely corrosive and corrosion-mechanical damages.

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