How it works
Electropolishing removes a microscopically thin layer from the steel surface using an electrochemical bath rather than abrasion — the result is a very smooth, bright surface with the peaks of the surface texture preferentially dissolved away.
How it differs from mechanical polishing
Mechanical polishing (buffing to mirror finish, see our finish guide) physically abrades the surface smooth; electropolishing dissolves it smooth. Electropolishing can reach into recesses and complex geometries that a buffing wheel physically cannot.
How it differs from passivation
Passivation cleans contamination and strengthens the protective oxide layer without meaningfully changing appearance; electropolishing changes both surface texture and appearance while also improving corrosion resistance. They serve overlapping but distinct purposes.
Where it's actually specified
Pharmaceutical, food processing and medical equipment — applications where surface smoothness has a hygiene function (related to the Ra values those industries specify). For architectural railings and cladding, it's typically unnecessary cost.