The first line of defense against corrosion is having an unperturbed native oxide film that serves as an effective barrier to moisture, oxygen, and other corrosive elements; as found in stainless steels and a few other alloys. However, for certain applications, stainless steels and most other alloys require additional surface protection against corrosion. Different types of surface films, coatings, or inhibitors can be used to form a protective barrier against corrosion. At CT&S, we can determine the inhibition efficiency of passivating films, coatings, or inhibitors selected for a given metal alloy and corroding environment.
Another form of corrosion inhibition is by cathodic protection, a cathodic polarization technique practiced to protect steel structures buried in soil or embedded in concrete exposed to marine or other aggressive environments. In Cathodic Protection, the metal structure is polarized cathodically using a sacrificial anode or by impressing a current with a direct current (DC )source.
New passivation methods have been developed in recent years using nano particle coating. Passivation using microporous oxide nanoparticle suspensions results in a largely improved corrosion resistance of stainless steel (SS), carbon steel, and aluminum. The metal oxide porous thin film is prepared from nano particulate dioxides of metals such as titanium, silicon, or zirconium. The top figure shows two stainless steel plates after exposure to moist air. The non-corroded bottom-half surfaces were coated with a film of nano particles, unlike the corroded uncoated top-half surfaces.
A metal surface coated with a nanoparticle coating can have a largely increased pitting potential, which translates in a substantial enhancement in pitting resistance. The green curve in the adjacent figure shows an increase of more than 0.5V in pitting potential for 316 SS coated with a nano particle oxide of zirconium, relative to the pitting potential of uncoated 316 SS (black curve). If you are interested in the microporous oxide application, contact us at MOST (608-345-6678).
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