Moisture Maintenance: Do You Have the Right Corrosion Prevention Plan?

The sea is calm, its gentle waves brushing the sugar-sand shoreline. In the distance, the rhythm of a steel drum echoes a familiar tune—“every little thing is going to be alright.” But appearances can be deceiving. Beneath the tranquil waters, a silent killer waits. Patient and methodical, it poses a constant threat to everything it touches.

Unlike a James Patterson thriller novel, one cannot see this killer until it is too late. Corrosion is indiscriminate in its attack—and none are exempt. For aircraft operators, constant diligence and proactive defense are essential. 

This Article First Appeared in FLYING Magazine

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FLYING spoke with three companies leading the charge in the ongoing battle against corrosion: Tropic Ocean Airways, the world’s largest amphibious commercial airline; Banyan Air Service, a full-service FBO maintaining aircraft in South Florida; and Pinnacle Aircraft Engines in Silverhill, Alabama, which knows all too well the effects that Gulf saltwater and tropical air have on powerplants.

Types of Corrosion 

Tropic Ocean Airways CEO Rob Ceravolo knows how to fly in tense situations.

As a former U.S. Naval aviator, and Top Gun graduate, Ceravolo piloted the legendary F-14D Tomcat in support of Operation Iraqi Freedom, earning him two Air Medals. He built his business on the foundation laid during his time spent in operations, safety, training, maintenance, legal, and administration. 

Asked how he kept his birds so clean and free of corrosion, he said it was simple. 

“We maintain our fleet like the Navy does,” Ceravlo said. “That and a whole lot of CorrosionX.”

His mission is working. Tropic Ocean Airways holds an Argus Gold rating, signifying the highest operational safety standard in the industry. 

Michael Jackson joined Tropic Ocean Airways in April as director of maintenance, responsible for the company’s Cessna Grand Caravan fleet. These high-wing workhorses, a mix of wheeled and amphibious (seaplanes), ferry people to the tropical paradises of Nassau, the Bimini Islands, and Exuma. 

• READ MORE: First Post-Maintenance Flight Should Be Treated With Caution and Respect

When asked about what a nightmare it must be to operate an aircraft in those types of climates, he offered a surprising answer.

“Some of these airplanes have been flying in the water every day for 10 years,” Jackson said. “But I don’t see a lot of corrosion internally on the airplane…We do see a little surface corrosion on the outer skin, particularly around the cowl latches. This is due to the dissimilar metals between aluminum and stainless-steel latches and hardware. You will also see it on fastener heads, as well as within the nut plates.” 

JD Kuti, the president of Pinnacle Aircraft Engines, said that corrosion due to operating so close to the Gulf can certainly be a challenge.

“I have corrosion conversations weekly,” he said with a laugh. 

Reciprocating horizontally opposed aircraft engines are chunks of steel and aluminum vibrating in unison. They get hot, cool off, and ingest who knows what from the environment. What could go wrong?

Most of the corrosion Kuti said he sees is on steel components, which get surface pitting, especially on the camshaft. It doesn’t take much to get started, so he recommends not delaying in addressing it for too long. Once you get rust and surface corrosion, it creates a pit inside. 

Combatting Corrosion 

Any warrior knows you can engage the enemy without a weapon. In this case, we don’t use guns or knives but grease and oil. 

When asked about the go-to protective coating, Jackson did not hesitate: LanoCote. Tropic Ocean mechanics install their screws with it, applying it around the thread like an anti-seize compound. Each screw is treated with the same care and attention as engine components because they’re stainless-steel screws being installed into steel nut plates set in an aluminum skin. 

Additionally, everything is coated with either a white lithium grease, LPS Corrosion Inhibitor, CorrosionX, or the company’s secret weapon, ACF-50. According to Lear Chemical Research, ACF-50 Anti-Corrosion Formula is a cutting-edge lubricant and corrosion inhibitor specifically engineered for the aerospace industry to treat metallic surfaces. This black magic concoction was not available when I practiced maintenance years ago. 

• READ MORE: Preparing for Unexpected, Inevitable Aircraft Maintenance Bills

Banyan Air Service takes a more traditional approach to corrosion prevention.

Eric Smith, MRO technical sales manager, and Danny Santiago, avionics director, were kind enough to discuss how they keep owners’ aircraft in pristine condition in South Florida. Alodine and anodizing are Banyan’s baseline for care. What is the difference? 

The AC43.13-1B teaches us that Alodine is a chemical process, whereas anodizing is an electric process. Banyan can apply Alodine in-house but subcontracts anodizing to an outside vendor. Any new metal work, such as sheet metal skin repair, is coated with Alodine, primed, and painted. 

Banyan, an authorized Pilatus PC-12 and PC-24 service center, sees these platforms roll through with a coating known as Mastinox. It must be effective because it coats the entire belly with it. According to the manufacturer, PPG, Mastinox is a nonchromate, corrosion-inhibiting jointing compound. Banyan will reapply as necessary on parts of a Pilatus, including reassembling components.  

At his engine shop in Alabama, Kuti swears by Amsoil Engine Fogging Oil (FOG). He encourages his clients to keep a can with them—you never know when you might need to sit your aircraft down for a while. He also advises when the aircraft is due for an annual inspection, so it can be taken to the mechanic. As soon as the inspection is complete, Kuti says the shop runs the engine up to temps, pulls a compression test, and then FOGs the engine.

Maintenance Inspections 

Tropic Ocean Airways boasts an adaptive maintenance program—and it learns something new every day. 

One key element is going above and beyond. Every postflight ritual includes a thorough washdown with a salt emulsifier, an engine wash and rinse, and the airframe panels are inspected every 25, 50, and 200 hours, respectively. While it’s true that Cessna has a maintenance program with recommended guidelines, most Caravans operate on the ground when taxiing and in the air. Tropic Ocean Caravans float in saltwater, which makes a significant difference.  

Cessna is not the only OEM in play here. Pratt & Whitney has a program in place for addressing engine corrosion, which includes a specific engine wash frequency. As mentioned earlier, Ceravolo set up his company to work like the U.S. Navy. Well, the Navy and Coast Guard wash those engines every single day—Tropic Ocean does too. 

Think critically about what’s happening under the maintenance program. When reviewing some of the inspection intervals, even in cases where the program only calls for a visual inspection, Tropic Ocean has made a deliberate decision, based on operational experience, to conduct more thorough inspections, often hundreds of hours sooner than required. 

Take the brakes, for example. They’re built with magnesium alloy calipers, which are highly prone to corrosion and won’t last in a saltwater environment. That’s why a significant focus during the 25-hour inspection is on the rotors, calipers, brake pads, and the wheel assembly itself. These components are constantly exposed to salt, and you can’t apply corrosion-inhibiting compounds to brakes—their performance would be compromised. Over time, you can see the metal being eaten away, almost like a sacrificial anode. That’s the level of exposure they are dealing with. 

When finished with the aircraft, it’s completely coated in white lithium grease. Every accessible bearing is treated to ensure there is always a protective barrier. One simply can’t leave any of it exposed in this environment. 

Banyan Air Service historically sees engine inlet corrosion issues. According to Santiago, it deals with several inlet-related issues, especially in turboprop aircraft. 

For example, for PT6-powered aircraft, if compressor washes are not performed regularly, corrosion will begin to attack the No. 1 inlet-bearing area. It’s a common and preventable problem. There’s also a need for special attention around lavatories and galleys, as these areas are frequent sources of hidden moisture and corrosion. 

Now, for operators flying under Part 91, this might not be as critical due to their lower utilization rates. But for high-volume charter operations, the situation is different. While they’re required to follow the maintenance manual, most also develop in-house procedures, specifically wash schedules and corrosion prevention. These internal programs often go beyond the manual and are tailored to their specific operational demands. 

For Pinnacle Engines, corrosion prevention begins on day one when an engine is in the shop. During assembly, Pinnacle technicians use manufacturer-specified oils and greases, as specified in the manuals. But here’s the challenge: The engines are run before delivery, so by the time they leave, much of that protective grease has already been flushed out by oil circulation. That’s why Pinnacle FOGs the engines before shipping. 

If an engine is going to sit for more than 30 days, Kuti says he always advises the customer to FOG the engines every 30 days for ongoing corrosion protection. Just as important, they need to cap all vents and openings to prevent air and moisture intrusion. This includes properly sealing the engine, muffler, and intake. 

Many people are unaware of the significant amount of moisture that can enter through the muffler. There have been cases where someone did everything right—they fogged the engine and capped all the obvious inlets yet still ended up with rusted cylinders. Why? Because the exhaust valve was open, allowing moist air to travel right through the tailpipe and into the combustion chamber. It’s a common oversight but a critical one to catch. 

Borescoping the cylinder barrels is always recommended and relatively straightforward. However, inspecting the camshaft is a much more complex process. Kuti said he typically doesn’t advise owner-operators to go as far as removing cylinders just to check the cam. It’s expensive, introduces unnecessary risk, and, if not done perfectly, can lead to more problems than it solves. 

In Kuti’s opinion, the most valuable and accessible inspection tool is the oil filter. You can learn a great deal from it. Do not rely solely on oil analysis, especially in cases where an engine has been idle for an extended period. Firing up a dormant engine just to taxi it to the shop can dislodge surface corrosion. If you take an oil sample after that, your analysis may show elevated levels of iron or steel, a false reading caused by harmless surface particles. That’s why I place much more value on filter inspection than oil analysis.

Always make sure to check the finger screen, too. Sometimes, what you find is finer than identifiable part numbers but no less telling. 

The key is to get the oil filter clean enough to perform a proper inspection. What technicians typically do is reroll the filter element, place it in a vise, and compress it gently. This pushes the oil out without releasing any embedded debris. Letting it sit under pressure in the vise allows the oil to drain while trapping any metal or contamination in place for accurate examination.

It’s all about getting a clean, undisturbed view of what the engine is telling you. 

Employee Training 

Tropic Ocean Airways trains its technicians in the same manner as the Navy does. 

It all starts with sealing the panels. Keeping water and moisture out of the airframe is critical. Every aircraft touched undergoes thorough cleaning and then complete refogging for corrosion protection. 

Tropic Ocean mechanics even apply corrosion preventative to the seat tracks after securing them, because passengers often board wet, straight from the water. That brings in salt, sand, and moisture, which can accumulate in those tracks and promote corrosion. Techs go in with brushes, clean them thoroughly, and reapply protective compounds to ensure they’re properly treated. 

The company also supports an apprenticeship program with Florida’s Broward County, where students work toward their A&P License. They’re directly involved in corrosion prevention work, under the guidance of a supervisor, learning correct rinse procedures, how to apply Salt-X, and finally, how and where to apply ACF-50.

This hands-on process teaches them a foundational principle: Maintenance starts with cleaning. If it’s not clean, you can’t properly inspect or maintain it. From there, they grow into more complex tasks, but it all begins with understanding the importance of cleanliness and corrosion control. 

Innovations and Technologies 

Banyan Air Service highlighted a solution from Quiet Technology Aerospace that replaces engine inlets on legacy aircraft.

The original inlet design utilizes an abradable liner. However, over time, especially when exposed to the elements without consistent washing after every flight, this material begins to lift and deteriorate. With months or years of exposure, this degradation progresses, and Bombardier provides a repair memo that allows you to remove the liner, often extending the component service life by an additional 100 to 500 hours, depending on the situation. 

On the standard Lear 60 inlet, Bombardier has since updated the inner liner material to aluminum, resolving the corrosion issues. This makes it a significantly better option for operators flying in corrosive environments, such as the Bahamas, South America, or the Caribbean, where the original material would be far more vulnerable. The aluminum liner has proven itself over time in these conditions. 

Similarly, Quiet Technology Aerospace addressed concerns on the Challenger 300 by applying a titanium finish to the thrust reverser (TR) buckets, a modification covered under a supplemental type certificate (STC). This upgrade significantly reduces the risk of corrosion in harsh environments. 

When I owned my engine shop, we had a decision regarding cylinder barrel options. Years ago, the two main choices were nitride steel and chrome. That changed when ECI entered the market with its nickel-coated CermiNil cylinders, which quickly gained popularity and shifted industry preferences. Eventually, ECI was acquired by Continental, and things changed again. According to Kuti, the ECI machine finished the barrels before applying the coating. 

However, Continental transitioned to a chemical-etching process, which enabled faster throughput but at the expense of reduced coating durability. As a result, Kuti said the coatings no longer hold up as they once did. 

What Pinnacle does now is take brand-new cylinders, disassemble them, and send them to Tulsa, Oklahoma-based Aircraft Cylinders of America (AAC). AAC applies high-quality nickel plating. The team reassembles and installs them. This provides the client with the performance and corrosion resistance they expect.

Operational Adaptations 

When it comes to flying in high-humidity regions like the Gulf, Kuti said he always emphasizes the “one-hour rule.” It applies to two key areas of engine care. 

First, never fly unless you can run the engine for at least one full hour. The goal is to raise engine temperatures high enough and sustain them long enough to burn off internal moisture, a natural byproduct of combustion. Short flights don’t allow the engine to reach the critical temperatures. Instead, they contribute to internal moisture buildup, which increases the risk of corrosion. 

Second, never preheat the engine for more than an hour. Many operators leave preheaters on for extended periods, thinking it’s beneficial. However, as ambient temperatures fluctuate, so do internal moisture levels, especially when attempting to maintain a constant temperature. That fluctuation can encourage condensation rather than prevent it. 

At Pinnacle, one of the first upgrades it made was installing climate control throughout the shop to reduce humidity. Despite that, it still sees freshly cleaned parts begin to rust within hours. After cleaning, the technicians typically move parts directly to magnetic particle inspection (magnafluxing) and avoid using oils or moisture-displacing sprays, such as WD-40, which would interfere with the testing process. 

Instead, Pinnacle uses a specific carrier fluid designed for inspection prep that provides a temporary protective layer without compromising the test. In environments like Pinnacle’s, moisture management is a constant concern, and following these small, disciplined steps makes a significant difference in the long-term health of the engine. 

Bottom Line 

This snapshot of three companies operating in challenging subtropical conditions highlights a common truth—preventing corrosion takes consistent, proactive effort. It all comes down to washing and treating, and then applying lubricant and greasing—every day if you have to.

Tropic Ocean Airways’ Jackson put it this way: “It is one thing to build a program, but you have to have self-discipline to do it.”

TThis column first appeared in the August Issue 961 of the FLYING print edition.