Cutting Down Corrosion

The easiest way to explain corrosion, without using large thirteen-letter words like, deterioration, is to give examples of what corrosion is like. For example, corrosion is like termites eating away at a block of wood. Corrosion is like how your teeth form cavities when you don't brush. It is also like the sun melting away the snowman you just made.

The corrosion in a military helicopter forms around the bolts that keeps the copter together.

Basically, corrosion is the break down of materials due to various factors.

But if you prefer the long version, with large thirteen-letter words, then corrosion is the deterioration of materials through various electrochemical, chemical, and environmental factors, according to a corrosion specialist at the University of Hawai`i College of Engineering, Dr. Lloyd Hihara.

Rust is a type of corrosion you are probably familiar with, but corrosion comes in various forms. General or uniform corrosion is when the entire metal corrodes at an even rate. Stress corrosion usually happens to a metal with good corrosion resistance, but it is under stress and in an unfriendly environment, which causes cracks to form in the metal. It is in these cracks where the corrosion forms. Pitting corrosion, which also occurs on metals with good corrosion resistance, occurs when the natural protection of the metal breaks down in small areas and tiny pits of corrosion form.

So how do we prevent corrosion? That is one of the issues Dr. Hihara has tackled with his research at the University of Hawai`i. However, to understand how corrosion can be prevented, we need to understand that most metals, like iron and steel, really don't want to be a metal. "All metal, in its natural state, is in the form of a dust-like oxide, which is also the product of corrosion," Dr. Hihara explains. "To turn the oxide into a metal, it takes a lot of energy for the refining process. When it is in the form of a metal, it has a tendency to want to turn back into its original state."

A typical place where corrosion forms, on an outdoor fence.

Dr. Hihara's current research includes creating a thin artificial ceramic film around metals to form a corrosion barrier. In certain metals, like titanium and aluminum, a natural oxide films forms around the metal, which seals the metal from further corrosion. However, on some other metals an oxide film forms on the surface, but it doesn't protect the metal. So this artificial ceramic film can create a protection barrier around those metals.

In his upcoming research project, Dr. Hihara will be teaming up with the United States Army to start up a corrosion research center here in Hawai`i. According to Dr. Hihara, the two major areas that will be studied at the corrosion research center will the corrosion of metal-matrix composites and the coupling of metal alloys to organic-matrix composites.

According to Dr. Hihara, metal-matrix and organic-matrix composites are advanced lightweight and durable materials. Composites like these are usually used to replace heavier parts on machines, like aircraft. "These composites are usually used for military aircraft. For example, some satellites use a graphite epoxy composite and the space shuttle uses boron aluminum composites," Hihara said.

However, these composites may be light and durable, but when two dissimilar materials are combined, like in metal-matrix composites and organic-matrix composites mixed with metal alloys, corrosion is accelerated.

Dr. Hihara hopes to find ways to prevent this corrosion from happening and give the Army useful information. "The Army is probably looking for new advanced material that can be used for improving their equipment, but they need to know how they hold up to environmental conditions," Hihara said. "Our research data will help them to decide what advance materials they can use on their equipment."

With help from Dr. Hihara's research, perhaps preventing corrosion will be an easy task like getting rid of termites with bug spray or stopping cavities with fillings or preventing your snowman from melting by sticking it in the freezer.





 

Entire contents of this web site © 1999-2005
University of Hawai'i at Manoa College of Engineering.
All Rights Reserved.

Problems, questions, comments?
Contact The Web Team