Determination of Bimetallic Corrosion Risk Using an Electrochemical Method

Abstract

The purpose of this study was to investigate (simulation of environment for salt treatment of roads in winter and the simulation of the environment of condensed exhaust gas) the galvanic corrosion phenomena which can exist in the construction coupling of cars. The electrochemical behaviour of the hot dip galvanized steel and aluminium alloy, stainless steel and aluminium alloy and stainless steel and silumin which were investigated by electrochemical methods in 3 % NaCl solution and in SEG solution. The open corrosion potential measurement was used to obtain the values of the potential for each couple. The measurement showed a greater bimetallic risk for hot dip galvanized steel with aluminium alloy, where there was ΔESCE > 500 mV and this couple is not suitable either for use in aggressive environment. Calculation of the rate of corrosion attack results from the determination of corrosion currents as measured by Taffel and Evans. The extent of corrosion damage was analysed by means of a light microscope. Keywords: bimetallic; aluminium alloy; stainless steel; silumin; exhaust gas; corrosion potential; electrochemical method;

Degradation of Components in Cars Due to Bimetallic Corrosion

“…The risk of formation and the extent of bimetallic corrosion of different metals can be assumed based on the “anode index” [ 15 , 16 ]. The open corrosion potential (OCP) measurement results are summarized in Table 5 .…”

“…Corrosion potential expresses the resistance of the surface of the material to its degradation in an aggressive environment. Changes in potential towards more positive values indicate the emergence of a protective layer of corrosion products that protects the surface from further corrosion attack (i.e., a passive layer has formed) [ 16 ].…”

“…The sample was polarized from an external source with direct current in a selected range of potentials, and the current density required to reach these potentials was determined. The corrosion rate depends on the kinetics of anode (oxidation) and cathode (reduction) reactions, while the calculation of the rate of corrosion attack is based on the determination of corrosion currents, determined by measuring [ 15 , 16 ]. The polarization resistance Rp was determined from the Stern polarization curve.…”

“…The polarization measurement methods based on electrochemical concepts enable us to determine the instantaneous corrosion rate at the electrode/solution interface by determining the exchange current density in the electrode equilibrium state and the corrosion current density in the corrosion system [ 15 , 16 ].…”

“…The difference in corrosion potential ∆E caused by the action of the corrosive environment on the steel surface was 498 mV at the end of measurement. The EN AW-6060 corrosion potential (in the couple with AISI 304) in SEG solution on the first day of measurement after 6 h slightly increased to the value −567 mV and in this potential range it stayed up to the 16th day of measurement, while from the 16th day of the test the potential decreased to the min value E SCE = −805 mV.The risk of formation and the extent of bimetallic corrosion of different metals can be assumed based on the "anode index"[15,16]. The open corrosion potential (OCP) measurement results are summarized in Table5.…”