Harrison EP takes great pride in all of the products that it has an opportunity to work on. Our passivation process improves surface function of materials such as: stainless steel, AL6xn, nickel, hastelloy, etc.
Passivation is a method of maximizing the inherent corrosion resistance of a metal surface (most commonly stainless steel) that is performed in post-fabrication. This process should not be confused with a topcoat or a scale removal treatment, such as pickling, but rather passivation is the process of making a metal surface passive. Creating a passive surface means that a film is formed over the metal surface causing it to lose its chemical reactivity with airborne contaminants and/or chemical agents. Passivation is commonly paired with Metal Pickling (or chemical descaling).
» Learn more about the differences between Passivation and Pickling.
Stainless Passivation Process
Chemical passivation is a two step process. First step uses acid (most commonly nitric acid) to remove any free iron or iron compound that may reside on the surface of your component parts. If any iron is left on the surface it will create a localized site where corrosion can continue. The process of using acid does not effect the surface when dissolving the iron and its compounds. The second step uses an oxidizer to force the conversion of chromium metal on the surface to the oxide form. This will create the uniform chromium oxide protective layer.
Advantages of using Citric Acid for Passivation
Citric acid has been used more commonly in recent years, because it is very effective at removing iron and compounds from stainless steel surfaces, and it is safer for the environment compared to nitric acid. Citric acid cannot oxidize chromium, which is the second stage of the classic passivation process that builds up a protective layer on the surface. The citric acid passivation process must rely on air oxidation, and is most commonly used on small component parts that will not be exposed to aggresive chemicals or environments. Below are more advantages that citric acid has over nitric acid:
- Citric acid is biodegradable
- Produces fewer effluent concerns
- Citric Acid is often used as a food ingredient
Chemical Passivating and it's Advantages
- Corrosion Resistance: passivation effectively removes surface contaminates in order to improve performance.
- Appearance: with no machinery actually coming into contact with the surface of the metal, passivation leaves it microscopically smooth.
- Restoration of Surfaces: as with any material, metal is susceptible to wear from any number of impacts, abrasions, erosion and corrosion.
- Deburring: electropolishing will simultaneously deburr and polish the surface.
- Cleanliness: after passivation the improved microfinish will reduce total surface area and contaminate adhesion.
- Endurance: since our processes remove cracks and other surface defects, the fatigue strength of a metal is improved. Seen most commonly in springs.
- Microsizing: electropolishing can be used as a method for sizing parts to close tolerances within 0.0001 inch.
- Inspection: electropolishing reveals the true microstructure of the metal and thus becomes an effective inspection tool.
Chemical passivation treatment removes free iron & contaminants and promotes the formation of a chromium-rich corrosion resistant layer...
Passivation and Pickling are two different processes, which produce different results...
Harrison Electropolishing has performed passivation treatments on AL6XN with excellent results for a number of years...
Surface contaminants, including grease, dirt, iron, and other imbedded metallic particles are removed during the passivation process...
The presence of exogenous surface contaminants may adversely affect the engineered corrosion-resistant properties of Nickel alloys...
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