Predicting corrosion with CFD

Having shown that computational fluid dynamics software can solve corrosion equations to identify especially vulnerable areas on aircraft, the engineering company Corrdesa of Georgia now hopes to convince airplane builders to adopt the technique in the design stage.

Modern aircraft have locations where two different materials must adjoin, such as a titanium fastener meeting an aluminum surface. When one of the materials has greater electric potential than the other, the one with less electrical potential acts as an anode and the other as a cathode. If the area is covered by a thin film of electrolyte, such as water condensed on an aircraft, electrons will flow through it, and the anode material will corrode.

The locations and rate of this galvanic corrosion are difficult to predict, so Corrdesa applied the Siemens STAR-CCM+ CFD solver to the problem, along with the unique polarization curves it derived for various materials through lab experiments. 

“CFD does not only relate to fluids in motion,” explains Corrdesa engineer Julio Mendez, who is in charge of developing methodologies for corrosion applications. “We use the same framework, but with different equations, [those] for galvanic corrosion.” 

The polarization curves are supplied to STAR-CCM+ by Corrdesa’s Corrosion Djinn database, he adds. 

Mendez says the technique correctly predicted where specific spots of corrosion would occur around the fuel access doors in the wings of U.S. Air Force C-17 cargo planes. The rate of corrosion, measured in microns per year, can be translated into a standardized scale of 1 to 5 — 5 for the worst corrosion potential. This month, Corrdesa plans to demonstrate the technique for the Air Force at Wright-Patterson Air Force Base in Ohio. 

Next, Corrdesa believes that if airplane designers incorporate the technique, they could adjust their geometries and choices of materials to head off expensive maintenance issues. Just as plane manufacturers have teams that design the plane’s aerodynamic shape and its cooling and electrical systems, Mendez expects they’ll soon employ an electrochemistry team to target corrosion. “That’s what we think the future will look like.”

With the “corrosion toolset,” as Mendez calls it, such a team could load in specific geometries and materials, and the toolset will spit out a prediction. 

About Keith Button

Keith has written for C4ISR Journal and Hedge Fund Alert, where he broke news of the 2007 Bear Stearns hedge fund blowup that kicked off the global credit crisis. He is based in New York.

FACT: Corrdesa’s name is short for “corrosion-resistant design by environmental stress analysis.” 

Predicting corrosion with CFD