The influence of barium chloride (BaCl \(_2\) ), sodium chloride (NaCl), potassium chloride (KCl), and calcium chloride (CaCl \(_2\) ) aqueous salt solutions on Rayleigh–Bénard double-diffusive magnetoconvection in bi-viscous Bingham fluids is investigated to understand how salt-specific diffusion and magnetic effects govern flow stability and heat–mass transport. The working medium is modeled as a bi-viscous Bingham fluid, and its thermophysical properties such as density, specific heat capacity, thermal conductivity, thermal diffusivity, and thermal expansion coefficients are obtained from experimental data and literature sources for various aqueous salt solutions containing BaCl \(_2\) , NaCl, KCl, and CaCl \(_2\) . A weakly nonlinear stability analysis based on Fourier series expansion was performed and the Ginzburg–Landau model was derived to quantify the heat and mass transfer. Worth concluding that the mean Nusselt number ( \(\overline{\hbox {Nu}}\) ) and mean Sherwood number ( \(\overline{\hbox {Sh}}\) ) are strongly influenced by the solutal Rayleigh number ( \(R_\textrm{S}\) ) and yield-stress parameter ( \(\beta \) ). Increasing the bi-viscous Bingham fluid parameter \(\beta \) enhances both heat and mass transfer, as evidenced by the increase in \(\overline{\hbox {Nu}}\) and \(\overline{\hbox {Sh}}\) . The observed transport hierarchy among BaCl \(_2\) , NaCl, CaCl \(_2\) , and KCl is primarily governed by intrinsic thermophysical properties such as thermal diffusivity, solutal diffusivity, density variation, and ionic mobility, which together control boundary-layer thickness and buoyancy-driven convection intensity. The destabilizing configuration ( \(R_\textrm{S} < 0\) ) leads to the formation of double-diffusive finger-like convection structures driven by the competition between thermal and solutal buoyancy forces together with differential diffusion effects.
