To get the subject back on track. Non corrosive and carbon brake friendly fluids are available.
Crumbling Corrosion Although GMIA made the switch to help fight winter conditions, the third-generation liquid deicer also helps combat aircraft corrosion problems associated with potassium acetate and potassium formate deicers. Using "better products" for its airline customers was an added bonus, Farmer explains.
Potassium acetate is the most common liquid deicing product used in North America, says Keith Johnson, president and CEO of deicing manufacturer Cryotech. According to Johnson, potassium acetate and potassium formate deicers have been used effectively for more than 20 years, but problems have surfaced regarding their corrosive nature.
Airlines link the following problems to potassium formate and potassium acetate deicers:
1. Carbon brake oxidation. Over the last 20 years, airlines have moved from steel to carbon brakes to reduce aircraft weight. Contamination from potassium can result in catalytic oxidation and subsequent carbon degradation in aircraft brakes. "Deicer fluid seeps in and works its way into the carbon on a microscopic level," Duncan explains. "As the brakes heat up, it generates a catalytic reaction causing hard carbon disc material to crumble. You cannot predict when this is going to happen. It proceeds quickly and can happen within a few flights."
The corrosion is a serious safety concern, because braking effectiveness is reduced as carbon breaks down, stresses Kelvin Williamson, North American president at Basic Solutions. "Pilots may not get the braking performance they expect," Williamson explains. "If an aircraft does a rejected takeoff, the plane may end up going off the runway."
Brake parts can actually fly off the aircraft and puncture aircraft wings, engines or other areas, he cautions. Carbon disc debris left on runways, taxiways or ramp areas can damage other aircraft.
Airlines have stepped up maintenance intervals to address these problems, he adds, but the extra service comes at a high price - up to $5 million more per year for some airlines. Industry wide estimates, Williamson reports, are as high as $75 million.
2. Cadmium corrosion. Field reports increasingly suggest contact with potassium-based deicers damages aircraft components, especially cadmium-plated ones. Boeing has noted cadmium corrosion on its 737NG aircraft, which has a bigger cutout in the wheel, Duncan points out. It is believed blow back during taxiing sprays deicing fluid onto the plane's cadmium connectors and causes corrosion. As wire bundles become brittle, they begin to arc, adds Williamson.
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