Pasivado

Pasivado is a term used in certain Iberian-language technical writings to describe the surface state of a metal that has undergone a passivation treatment. In general, pasivado corresponds to the English term passivated: a metal surface with a protective, adherent oxide film that reduces reactivity and corrosion in hostile environments. The term is most commonly encountered in Portuguese- or Spanish-language sources, where it is treated as an adjective or noun referring to a passivated surface or the passivation state of a component.

Process and applications: Passivation involves chemical or electrochemical treatments that selectively remove free iron from stainless steels, promote the formation of a chromium-rich oxide film (primarily Cr2O3), and otherwise form protective layers on alloys such as aluminum or titanium. Common agents include citric acid or nitric acid for stainless steel, with specific formulations for other metals. Electrochemical methods, including controlled voltammetry or anodic oxidation, can enhance the protective layer. Pasivado surfaces are relevant in industries such as aerospace, medical devices, and chemical processing where corrosion resistance and, in some cases, biocompatibility are essential.

Characteristics and limits: A pasivado surface is not immune to attack; the protective layer can be damaged by mechanical abrasion, high temperatures, or aggressive chemicals. The quality of passivation is typically assessed by standardized tests and visual inspection. In stainless steel, standards such as ASTM A967/A967M guide chemical passivation procedures and acceptance criteria.

See also: passivation, corrosion, oxide layer.