Corrosion resistance property will be more in coarse grain structure.

Detailed Explanation

Grain size is an important parameter that determines the mechanical properties and corrosion behavior of a material.

These coarse-grained regions formed via elemental diffusion towards the inter-particle pores during the HIPping process.

Smaller grains have greater ratios of surface area to volume, which means a greater ratio of grain boundary to dislocations. The more grain boundaries that exist, the higher the strength becomes.

Grain boundaries are susceptible to corrosion. Coarse grain structure has fewer grain boundaries and thus has greater corrosion resistance.

At the smaller grain size (∼14 μm), the strain hardening is improving the mechanical properties. While increasing the grain size, e.g. up to ∼168 μm, the corrosion rate increases due to less grain boundary volume and accordingly less dense passive layer