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Corrosion Behavior

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Atmospheric Corrosion of Aluminum Alloys

Relative humidity, temperature, sunshine, pollutants, salinity all play a significant role in the atmospheric corrosion rate of materials and when very specific conditions are taken into consideration e.g. subtropical marine environments, can result in some of the most extreme corrosion conditions possible.
As one of the most widely produced metals on the planet, aluminum is the subject of many investigations in this area with at times, some interesting results.

Atmospheric Corrosion Resistant CORTEN Steel

Weathering means that due to their chemical composition steels exhibit increased resistance to atmospheric corrosion compared to unalloyed steels. The corrosion retarding effect of the protective layer is produced by the nature of its structure components and the particular distribution and concentration of alloying elements in it.

Bimetallic Corrosion

Bimetallic corrosion is the phenomena by which preferential corrosion will appear between two joined metals of different galvanic status with the corrosion attacking the anodic metal.
The most common way to protect against bimetallic corrosion is by relatively simple use of plastic or rubber as dielectric insulators.

Cast Stainless Steels

Stainless steel castings are usually classified as either corrosion-resistant castings or heat-resistant. The usual distinction between heat-resistant and corrosion-resistant cast steels is based on carbon content.
Cast stainless steels are most often specified on the basis of composition using the designation system of the High Alloy Product Group of the Steel Founders Society of America (the Alloy Casting Institute).

Cavitation Erosion

Cavitation Erosion is a localized form of erosion caused by repeated small or large impact pressures which lead to pitting, initially on a granular level.
Testing of resistance to cavitation erosion is a well-documented subject with the main measurement indicators being the change of cumulative erosion rate (The amount of mass losing in unit time) with time.

Corrosion and Corrosion Properties of Stainless Steels: Part One

Stainless steels are stainless because a protective layer spontaneously forms on their surfaces and reduces the rate of corrosion to almost negligible levels. Under normal conditions, this layer heals very rapidly if scratched, so that if stainless steels only suffered from uniform corrosion, they could survive for literally millions of years.
This thin, invisible surface layer is an oxide that protects the steel from attack in an aggressive environment. As chromium is added to steel, a rapid reduction in corrosion rate is observed to around 10% because of the formation of this protective layer or passive film.