We present a corrosion internal state variable (ISV) damage model based upon the integrated computational materials engineering (ICME) hierarchical multiscale paradigm. Structure–property experiments for magnesium alloys were used where the only inputs were the volume fractions of each element of the periodic table. This macroscale ISV corrosion model finds its basis in Horstemeyer’s mechanical damage model, which includes three separate ISVs for damage nucleation, growth, and coalescence, as well as Walton’s inclusion of corrosion, which introduces five new ISVs for pit nucleation, growth, and coalescence, along with general corrosion and intergranular corrosion. While Walton’s corrosion ISVs are phenomenological in nature, herein we develop a multiscale physical basis for the corrosion ISVs. The parameters for the macroscale corrosion ISVs were garnered from the mesoscale Butler–Volmer equations. Pure magnesium with differing amounts of aluminum were used in corrosion tests to exemplify the different pitting, general corrosion, and intergranular corrosion rates, and the macroscale ISV model was calibrated with said data, in which the only inputs to the model are the volume percentages of the elements magnesium and aluminum. Although magnesium alloys were used to motivate and calibrate the model, the model is abstract enough to possibly capture other material systems as well.

A new experiment was conducted to determine the corrosion rates of different geometric structures (vertical plate, horizontal plate, cube, and sphere) with the same surface area of pure magnesium in a saltwater immersion environment of 3.5% NaCl for 108 h, illustrating a clear geometry effect arising from local boundary layer water flow. Magnesium was chosen as an idealized material because of its small electrochemical potential. The different corrosion mechanisms were analyzed and quantified by measuring the surface roughness (localized corrosion) via laser profilometry, mass loss (general corrosion) by weighing specimens, localized and intergranular corrosion via Scanning Electron Microscopy and Optical Microscopy, and total corrosion via hydrogen measurements. Although the corrosion rates were very similar at the beginning of the tests, the vertical and horizontal plates gave corrosion rates greater than the cube and sphere shortly after the tests started. Water circulation induced by hydrogen gas bubbles caused a greater corrosion rate at the edges of the plates and cube. These results indicate that a structure’s geometric edges should be made smoother to lessen corrosion effects in design. Also, when one is designing for corrosion resistance of a structural component, our results demonstrate that the designer must consider the fluid dynamics in the boundary value problem surrounding the structural component, since the geometric shape changes the corrosion rate.