www.aip.org/radio/scripts/corrosion.txt

Part of content: Corrosion!

(sfx: old jalopy sounding car)

WE SEE UNSIGHTLY RUST ALMOST DAILY ON OLD CARS OR CORRODED PIPES.
BUT ITS MORE THAN UGLY--RUST CAN BE DOWNRIGHT DANGEROUS. THE ALOHA PLANE
CRASH SEVERAL YEARS AGO, WHEN THE ROOF OF THE PLANE PEELED OFF LIKE A
CONVERTIBLE TOP, WAS DUE TO CORROSION IN THE METAL. IN A CHEMICAL PLANT,
RUSTED PIPES CAN LEAK HAZARDOUS WASTE INTO THE GROUND. ON A BRIDGE, A
CORRODED SUPPORT COULD BE FATAL. BUT CORROSION CAN BE NEXT-TO-IMPOSSIBLE
TO FIND IF ITS HIDDEN DEEP WITHIN THE METAL. PHYSICIST NANCY DEL GRANDE AT
LAWRENCE LIVERMORE NATIONAL LABS SAYS INSPECTORS NEED TO BE ABLE TO FIND
CORROSION EVEN WHEN THEY CAN'T SEE IT.

Del Grande: "We're . . . developing technologies that would help people . . .have infrared vision
just like superman's x-ray vision, to see through structures and . . . all sorts of materials to find flaws that
are not visible."

TO EXAMINE THE INSIDES OF A STRUCTURE, SAY AN AIRPLANE, DEL GRANDE
FLASH HEATS A SECTION OF THE PLANE AND THEN TAKES INFRARED PHOTOGRAPHS OF
THE METAL, AS IT COOLS. INFRARED PHOTOS REVEAL THE TEMPERATURE OF THE
METAL AT ANY PARTICULAR TIME. TEMPERATURE IS IMPORTANT BECAUSE IT
CHANGES DEPENDING ON HOW THICK THE METAL IS, WHICH IN THIS CASE TELLS YOU
HOW CORRODED IT IS. JUST AS A SMALL ICE CUBE MELTS FASTER THAN A LARGE
BLOCK OF ICE, A THIN SHEET OF ALUMINUM CHANGES TEMPERATURE MORE QUICKLY
THAN A THICKER SHEET.

Del Grande: "Where there's less metal it gets hot faster and loses heat faster. . . it changes
temperature wildly, it swings."

BY RECORDING THESE TEMPERATURE CHANGES IN INFRARED PHOTOS, AN
INSPECTOR CAN DETERMINE HOW THIN--OR HOW CORRODED--THE METAL IS. A LITTLE
CORROSION DOESN'T MEAN THE PLANE'S WING WILL RIP OFF ON IT'S NEXT FLIGHT, SO
THE INFRARED IMAGES GIVE BACK PERCENTS ON JUST HOW BAD THE CORROSION IS,
LETTING INSPECTORS KNOW IF IT'S TIME TO REFIT THE AIRPLANE OR NOT. THE
INFRARED TECHNOLOGY IS ONE OF SEVERAL CURRENTLY BEING EXAMINED TO
COMBAT CORROSION, BUT HOPEFULLY SOON THERE WILL BE NO PLACE LEFT FOR RUST
TO HIDE.