Numerical simulation of the aluminum–zinc–steel galvanic system for new designs of automotive chassis

Abstract

The requirement for lighter vehicles in the automotive industry promotes designs based on the combination of different metallic alloys. Such an approach, however, leads to galvanic‐corrosion risks, which compromise the durability of vehicles. One proposal to minimize such risks is to separate some of the chassis components by a Zn washer. The present work uses the finite element method to evaluate such an innovative design. The capacity of the washer to protect its aluminum alloy and carbon steel neighbors is assessed. As a worst‐case scenario, the bare metals are in contact with NaCl solution. Two electrolyte layer thicknesses are assumed: in the micrometer and in the millimeter range. Each case requires different mathematical models. For the thin film case, the zinc washer is able to protect its neighbors from corrosion. However, it sustains large corrosion rates, and thus its protection is effective only during short periods. Furthermore, as the Zn surface degrades and thus recesses, the “protective field” is blocked by the neighboring metal‐walls. The thicker the electrolyte layer, the weaker the Zn protective capability and, at some point, the corrosion of the aluminum alloy is unavoidable.

Acidification of the electrolyte during the galvanic corrosion of AA7075: A numerical and experimental study

“…16,36 This allowed addressing numerical issues commonly encountered during the FEM implementation of a two-dimensional (2D) domain with one geometrical length much smaller than other (e.g., a large electrolyte [cm] with a thickness up to some microns). 16,17,37,38 Such a source term is expressed by a relation between the molar flux and the electrolyte thickness. It is defined for the only two electroactive species considered in the model (i = OH − and i = Al 3+ ), which are described as follows:…”

“…From the numerical point of view, they are piecewise interpolations of the experimental curves. 16,38,39 The final governing equation takes the form:…”

Micro‐galvanic corrosion of duplex stainless steel annealed at different temperatures evaluated by experiments and a numerical simulation model

“…The area ratio of the cathode and anode was L α /L γ , which has been adopted by many researchers. [24][25][26]28,34] Different ratios of L α /L γ represent the proportions of the two phases in the DSSs at different annealing temperatures. According to the phase ratios of the DSSs annealed at different temperatures, the lengths of the phases in this model were set as shown in Table 1.…”

“…Experiments [20,21] and numerical simulation models [22][23][24][25][26] are usually used to investigate galvanic corrosion. Experiments usually include morphology observation, [27] polarization curve measurement to predict the galvanic potential and galvanic current density through the superposition of polarization curves, [28] zero resistance ammeter (ZRA) to measure the galvanic current density between materials, [14,15] and the scanning vibrating electrode test.…”

“…Experiments usually include morphology observation, [27] polarization curve measurement to predict the galvanic potential and galvanic current density through the superposition of polarization curves, [28] zero resistance ammeter (ZRA) to measure the galvanic current density between materials, [14,15] and the scanning vibrating electrode test. [24,25,27] Numerous studies [20,22,24,26,29] demonstrated that numerical simulations are accurate in predicting galvanic corrosion. The area ratio of the cathode and anode, properties of the solution, and potential of the anode and cathode affect the galvanic corrosion of materials.…”