Aircraft corrosion: Fighting corrosion of the grounded Boeing 737 Max fleet

Airplane crashes are rare and tragic occurrences. Despite their rarity, the two deadly Boeing 737 Max crashes in Ethiopia and Indonesia within five months of each other in late 2018 and early 2019 caused the deaths of all 346 people onboard both flights and massive changes in the industry.

Soon after the March 2019 Ethiopian Airlines crash, airline operators and regulators around the world began grounding their 737 Max planes, according to NPR. Currently, all 387 planes are grounded and sit dormant at hangers and airstrips around the world, waiting for regulators to decide to put them back into the air.

While the grounding of these aircrafts has restored confidence in the general public regarding the safety of flights on the 737 Max, operators are left with 387 dormant planes around the world, which presents a new challenge: fighting corrosion.

Fighting corrosion of the grounded Boeing 737 Max fleet
The tragic crashes have left these 387 previously active aircrafts sitting used at locations across the globe. An additional 200 737 Max planes are still in storage because Boeing is unable to deliver them while talks are still underway

No matter the outcome of the 737 Max aircraft's fate, airplanes are meant to fly, not remain in storage for prolonged periods of time. Jeremy Bogaisky at Forbes writes that this five-month grounding has led to a "small army of maintenance staff" working hard to fight off corrosion and other problems.

David Querio, president of Ascent Aviation Services, told Forbes that workers typically visit planes held at storage yards once a day to ensure all coverings on the hull are in good shape. 

According to Boeing's 737 maintenance manual, there are plenty of scheduled maintenance procedures workers follow for dormant planes to avoid them falling into disrepair. From protective coating sprays on unpainted metal surfaces to windshields being covered with reflective materials, there is still plenty of maintenance procedures to follow for unused planes.

Regarding corrosion, the manual requires technicians to scan planes for corrosion every week. When inspecting these aircraft, the Aviation Safety Bureau states the main areas are prone to corrosion and require close monitoring include: battery compartments, wheels and landing gear, wing flaps, cooling air vents, water entrapment areas and areas hit by exhaust stream.

For long-term storage, industry experts require the engines to be "pickled," which involves the oil being drained and replaced with an oil-corrosion prevention solution.
Though Boeing expects aviation officials to approve its changes to the aircraft by sometime later this year, various delays and technical problems have led to some in the industry thinking that this five-month delay could last significantly longer.

For example, Southwest Airlines and Air Canada have taken the plane off their flight schedules until after the new year. Even if the planes do get the approval from the U.S. Federal Aviation Administration, a Southwest spokesperson said it would take an estimated 120 hours of work per plane to ready the aircrafts to fly once again. This timeframe could result in 30 to 60 days worth of work to prepare the operator's entire fleet.

Fighting aircraft corrosion with CPCPs
Fighting airplane corrosion is not limited to the grounded 737 Max fleet. Corrosion is a huge issue facing the aircraft industry, as it can not only cost operators millions in inspections and repair work but can cause serious safety risks if left untreated or improperly handled. For this reason, technicians and mechanics are always on the lookout for any hint of corrosion.

According to the Federal Aviation Administration's 2018 Advisory Circular on corrosion control, aircrafts are exposed to various corrosive environmental elements, which can lead to quick corrosion degradable. For this reason, the way to approach corrosion care should not be taken lightly.

The agency advises that the sheer possibility of any in-flight problems or excessive downtime due to structural repairs caused by corrosion mandates a need for a thorough and active corrosion prevention and control program (CPCP). While the exact nature of the program depends on the aircraft and flying environment, the basic premise of a CPCP should allow for the regular cleaning, inspection, operational preservation and lubrication of the aircraft.

Other key premises of an effective CPCP include: well-trained personnel; early detection and repair strategies, periodic lubrication and preservation efforts; removal or repair of damaged protective coatings; quick treatment after detection; accurate recordkeeping and reporting; and the use of appropriate equipment and materials.

Following the tragedy surrounding the Boeing 737 Max crashes, it is imperative for all stakeholders to prioritize aircraft maintenance and safety measures, especially when it comes to fighting corrosion. Though corrosion can easily become a serious problem, with proper care and scheduled inspections, pilots, crew and passengers can continue to fly with confidence.