First principles calculation of the influence of different concentrations of Cl element on the corrosion resistance of tin and silicon-doped aluminum alloys

Al-Sn-Si self-lubricating bearing liners for engines suffer severe corrosion from Cl - infiltration under complex working environments. Most prior studies only conduct macroscopic tests at fixed Cl - concentrations, without atomic-scale insight into concentration-corrosion mechanisms of Sn/Si-doped Al-Sn alloys. This paper integrates DFT first-principles simulations and multi-scale experiments to investigate the anticorrosion behavior of single/co-doped Sn-Si Al matrix and Al/Al 2 Cu interfaces under variable Cl - contents. Surface energy calculations screen high-activity Al(210) and Al2Cu(111) planes, and stable Al(111)/Al2Cu(100) interfaces are built for doping and Cl - adsorption simulations. Doping dissolution energy confirms Sn possesses higher thermodynamic stability: Sn generates compact SnO 2 passivation film to capture Cl - , while porous amorphous SiO 2 from Si creates Cl - diffusion paths and aggravates substrate corrosion. Adsorption energy reveals Sn effectively immobilizes Cl - at low coverage; at high Cl - loading, Sn’s electron transfer saturates and Si competes for active sites, destroying the protective film. Electrochemical tests in 1%, 2%, 3% NaCl show the alloy exhibits the best corrosion resistance in 1% NaCl (minimum I icorr =2.7×10 -4 A/cm 2 , maximum charge transfer resistance). At 3% NaCl, corrosion rate rises by one order of magnitude to 10.9 mm/a due to Cl - breakthrough of passivation film and surface delamination. SEM, TEM, EDS verify rod-shaped incoherent Al 2 Cu precipitates, spherical Si phases as pitting origins, and passivation films composed of Al 2 O 3 and SnO 2 . Combined calculations and experiments determine the alloy’s Cl - tolerance limit of 2% – 3% NaCl, offering theoretical support for developing highcorrosion- resistant self-lubricating Al-Sn-Si bearing alloys.