Casa » Passivation

Passivation

1850
  • Christian Friedrich Schönbein

Passivation is the process by which a material becomes ‘passive,’ meaning it is less affected by environmental factors such as corrosion. It involves the spontaneous formation of a very thin, non-reactive surface film that acts as a barrier, shielding the bulk material from further attack. This film is typically an oxide or nitride layer, a few nanometers thick.

The mechanism of passivation is electrochemical. When a reactive metal like chromium, aluminum, or titanio is exposed to an oxidizing environment (like air or certain acids), its surface rapidly oxidizes. If the resulting metal oxide is stable, dense, non-porous, and well-adhered to the metal surface, it forms a protective passive layer. This layer is extremely thin, often only 1-3 nanometers, but it is sufficient to dramatically slow down the rate of corrosion by preventing direct contact between the metal and the corrosive environment.

The stability of this passive film is dependent on the environment, particularly pH and the presence of certain ions like chlorides. For example, the chromium oxide ([latex]Cr_2O_3[/latex]) layer on stainless steel is highly effective in many environments but can be locally broken down by chloride ions, leading to pitting corrosion. The breakdown and reformation of this passive layer is a dynamic process. If the film is mechanically scratched or damaged, the exposed metal will often repassivate almost instantly, a property known as self-healing.

Passivation can be a natural process or can be enhanced artificially through chemical treatments, such as dipping stainless steel in nitric or citric acid to remove free iron from the surface and encourage the formation of a more robust chromium-rich oxide layer. This process is distinct from applying a rivestimento, as the passive layer is formed from the base metal itself.

UNESCO Nomenclature: 3314
– Materials science

Tipo

Chemical Process

Disruption

Foundational

Utilizzo

Widespread Use

Precursors

  • Discovery of reactive metals like chromium and aluminum
  • Early observations of metals resisting corrosion in specific acids
  • Development of electrochemical theories

Applicazioni

  • stainless steel’s resistenza alla corrosione (chromium oxide layer)
  • titanium’s biocompatibility in medical implants (titanium dioxide layer)
  • anodizing of aluminum for protection and color
  • protecting silicon wafers in microelectronics

Brevetti:

QUELLO

Potential Innovations Ideas

Livelli! Iscrizione richiesta

Per accedere a questo contenuto devi essere un membro di !Professionals (100% free)!

Iscriviti ora

Siete già membri? Accedi
Related to: passivation, passive film, corrosion resistance, stainless steel, chromium oxide, titanium, anodizing, surface science

Lascia un commento

Il tuo indirizzo email non sarà pubblicato. I campi obbligatori sono contrassegnati *

DISPONIBILE PER NUOVE SFIDE
Mechanical Engineer, Project, Process Engineering or R&D Manager
Sviluppo efficace del prodotto

Disponibile per una nuova sfida con breve preavviso.
Contattami su LinkedIn
Plastic metal electronics integration, Design-to-cost, GMP, Ergonomics, Medium to high-volume devices & consumables, Lean Manufacturing, Regulated industries, CE & FDA, CAD, Solidworks, Lean Sigma Black Belt, medical ISO 13485

Stiamo cercando un nuovo sponsor

 

La tua azienda o istituzione si occupa di tecnica, scienza o ricerca?
> inviaci un messaggio <

Ricevi tutti i nuovi articoli
Gratuito, no spam, email non distribuita né rivenduta

oppure puoi ottenere la tua iscrizione completa -gratuitamente- per accedere a tutti i contenuti riservati >Qui<

Historical Context

(if date is unknown or not relevant, e.g. "fluid mechanics", a rounded estimation of its notable emergence is provided)

Related Invention, Innovation & Technical Principles

Torna in alto

Potrebbe anche piacerti