UNO Researchers Develop Nontoxic Technology Against Corrosion

Wednesday, January 26, 2000
University of New Orleans (UNO) researcher Al Daech is afraid of heights; not a good phobia to have when your research involves space shuttles, fuel tanks, and other, big, space-age equipment. He's been trying to conquer his fears since 1981. That's when his work on corrosion fighting collided with his fear of heights. As a Martin Marietta (now called Lockheed Martin) consultant, Daech found himself on a narrow bit of scaffolding 450 ft. in the air, inspecting one of the external fuel tanks on STS-I Columbia, the first space shuttle. Three days before the launch, a pool table-size blister formed in the external tank of the STS-I. Daech's inspection showed an oily rag wiped across the tank caused the blister. He and a crew immediately went to work. They applied a reformulated corrosion inhibitor to the tank - remedying the problem and increasing the life span of the metal. Three days later, with Daech's feet planted firmly on the ground, STS-I started a new era in space as the U.S. launched the first space shuttle in history. Years later at NASA, new knowledge and extreme circumstances in space caused Daech to reevaluate corrosion protection. Upon discovering a material in space called 5eV atomic oxygen that corroded metals and materials more severely than on earth, Daech and others sought alternatives to combat corrosion and create new coatings. "The atomic oxygen was eating the coating and even some of the plastic. Until then, I had never seen corrosion like this," Daech recalls. The first step in addressing this problem: simulate space. Take an atom of oxygen, make it go 17,000 miles an hour, and hit a surface to simulate what happens in space. After developing the first simulator of atomic oxygen degradation of aerospace materials for NASA, Daech was then able to work on a new corrosion-resistant coating; essentially a protective paint that's applied to the external fuel tanks on the space shuttle. The coating - still used today on the space shuttle - has since been adopted by other aerospace companies. "Eventually, we discovered we could alloy non-traditional metals into aluminum and make them corrosion resistant," Daech explains. Corrosion Definition Corrosion happens when oxygen and moisture mix, creating what we usually think of as rust. When you seal out the moisture and oxygen, you protect the object from that corrosion. It can't oxidize and thus its life is extended. "Corrosion is one of the biggest losses the nation endures in terms of materials. And the energy losses resulting from the corrosion are also tremendous," said John Crisp, dean of UNO's College of Engineering and executive director of the University of New Orleans Gulf Coast Region Maritime Technology Center (GCRMTC). Ships, bridges, and other marine structures all need to be corrosion-proof. In the past, various chromium-based inhibitors (in other coatings) have been applied to aluminum surfaces. These include strontium chromate, zinc chromate, and chrome phosphate. But these are heavy metal-based and largely carcinogenic. In addition, the EPA has shown the lead-based coatings were causing health complications in children. The import of the information from the EPA proves stunning. Small amounts of chromic acids or potassium dischromate can cause kidney failure, liver damage, and blood disorders. Chromate mists entering the lungs may eventually cause lung cancer. In most instances, these chromium-based compounds are now prohibited. At lower valences, (the EPA quantifies lower valences from chromium as "chrome three" or below on a daily, allowable pollutants-emissions level), chromium is considered non-carcinogenic. So when current coatings containing chromium must be refurbished - such as on military and civilian airplanes - the entire plane must be disassembled and treated to convert the chromium substance from "chrome six" to "chrome three." Only then can the plane be cleaned and repainted. The process requires all the parts and metal be washed and the water filtered into a sanitary disposal system for storage or discarding. The conceivable health effects are so serious that the runoff from a plant or its sewer is limited to one part per billion of the chromium, an almost immeasurable amount. In fact, chromium is so dangerous regulators limit chromium and chromates in coatings more severely than cyanide and some poisonous gases. Today's Application In the current wave of environmental prudence and cost-cutting consciousness, Daech, Dr. Nikhil Sarkar from the Louisiana State University Dental School (who worked on the adhesion aspect of the research), and researchers at GCRMTC have developed a new, environmentally-friendly corrosion inhibitor. "Corrosion costs the government billions of dollars on military aircraft, ships, vessels, torpedoes, and other things. With some of the current inhibitors found to be toxic, UNO's inhibitor could be a great cost-saving, environmentally-conscious benefit," says environmental engineer Bill Strasburg of John J. McMullen Associates, Inc. and a retired civilian Navy employee, who directed the UNO inhibitor testing for NavAir. According to the Naval Surface Warfare Center, it costs the Navy approximately 500 million to drydock ships a year, including 80 million for paint removal and replacement alone. The new corrosion inhibitor, an environmentally friendly coating for aluminum, has other benefits besides combating rust. It is not carcinogenic. It applies easily. And that means it's more worker friendly, safer for the environment, and will help control hazardous material costs, disposal, and handling. Using his more than 40 years of experience, Daech - along with UNO researchers - focused on creating a new pigment (for a reformulated coating) which is both effective in corrosion prevention in aluminum, and is environmentally acceptable. First, the collaborators created a sample coating (paint) that was applied to hand-cleaned aluminum alloys. The adhesion quality ranged from good to outstanding. When the coating was examined by an independent testing organization, which administered an ASTM-117B (American Standard Testing salt fog) test for 168 hours on scribed panels, no corrosion occurred. The test also revealed UNO's coating inhibited corrosion as much as chromium without the hazardous materials. "What we have to offer is something that tested better than anything in the world," says Daech. "This also complies with environmental regulations, plus it has the capability to eliminate the problem of carcinogenic coatings." OSHA has reportedly levied $10,000-a-day fines against companies when chromium invaded the water supply. "Remember, the entire fleet of military and commercial planes are protected from corrosion by chromates in coatings. The new UNO inhibitor could help with the problem. The coating could prevent corrosion while boasting an environmentally friendly status," adds Strasburg. Currently, naval researchers in Washington, D.C. have moved the inhibitor research from the 6.1 stage (laboratory) to 6.2 stage (pilot program). "This research is innovative. It has great potential. The commercial application would help with pollution and waste. It could solve a lot of hazardous materials' problems. This contains no hazardous materials," says Dr. Azar Nazeri, research engineer at the Naval Research Lab in Washington, D.C. Montgomery Pitman is a writer for Quest, a publication of research, technology and scholarly activity at the University of New Orleans. For information on subscribing to Quest, contact Joseph White, editor, at 504-280-6622, jewhite1@uno.edu
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