Ownership: Bust the rust

Those 50-year-old childhood memories recently flashed back while running my fingers over some rust-pitted steel cylinders near Seattle. There may be a political divide between the West Coast and Deep South, but rust is the same in both places, and it’s expensive everywhere.

This orange-colored corrosion results from iron being exposed to oxygen, moisture, and combustion byproducts during extended periods of inactivity. That’s why cylinder endurance is rarely a problem for flight schools, commercial operators, or active partnerships. However, many airplane owners barely fly 50 hours annually and are at risk of having their engines rot from within.

Running an engine on the ground for short periods is worse than letting it sit. Lots of moisture gets sucked in, but operating temperatures stay too low to burn it off. The best strategy is to fly for an hour and make sure the oil temperature gets to 180 degrees Fahrenheit or above.

I’ve been researching this while preparing to rebuild my Mooney’s engine. To keep it from costing me more money or anxiety when I can’t fly enough, I want to eliminate any chance of my new cylinders rusting. Evidence suggests the best solution is nickel silicon carbide electroplating, more commonly called “nickel plating.”

Cylinders in my current engine were “chromed” roughly 300 hours ago. The last three oil tests show fast-rising levels of that metal, suggesting chrome is flaking off the walls. My veteran mechanic says, “Chrome is trash!” but he endorses that hard metal for low-compression radial engines. Others have different opinions so personal research is highly recommended, since it’s a proven option that also looks great on hubcaps.

To my knowledge, the only legal choices for nickel-plated airplane cylinders are aftermarket electroplating by Aircraft Cylinders of America in Tulsa and new “NiC3” cylinders from Continental Motors in Mobile, Alabama. That manufacturer has FAA approval to produce Continental components, parts approved for Lycoming engines, and Experimental engines and components under the Titan name.

A number of well-regarded engine shops I spoke with buy new NiC3 cylinders from Continental, or purchase Superior or Lycoming jugs and have them plated in Tulsa for around $300 each, plus shipping. Anyone going that route should ask how aftermarket mods affect the manufacturer’s warranty. RAM Aircraft’s website says the company’s “Nickel New Cylinder Package cylinder assembly” is warranted for one year from the shipping date. It also warrants the cylinder bore to remain corrosion- and wear-free for five years.

Aircraft Cylinders of America Production Manager James Pitts told me they started nickel plating because customers asked for it, but added the company’s owner and he are chrome fans.

“It’s been around forever and we think it’s dependable,” he said, adding that chromed cylinders can be re-plated numerous times, whereas nickel can’t.

Personally, I’m getting all new NiC3 cylinders from Continental for four reasons.

First, it only costs $175 extra for each cylinder. That’s cheap insurance from a company that’s manufactured millions of cylinders.

Second, I prefer having one organization in charge of a product from start to finish. I also want to feel confident the company will be around for decades. Continental has been producing engines since 1929, appears well capitalized, and keeps innovating.

Third, NiC3 coatings were developed more than 50 years ago for high-performance sports cars. The material has proven durable and effective over tens of millions of hours. Plus, it’s far easier to break in than chrome, which can make a huge difference when it comes to long-term performance and oil consumption.

Fourth, the company’s industry-leading warranty is for 24 months or 1,000 hours, whichever comes first. Cylinder barrels are warrantied to be free from wear or corrosion for five years.

Seeing is believing

When business recently took me to New Orleans, I drove two hours northeast to Mobile where I could talk with some of Continental’s engineers.

Continental acquired San Antonio-based PMA parts manufacturer Engine Components International (ECi) in 2015. The FAA had granted ECi permission to improve existing technology and sell the results as proprietary if it met ASTM standards. This allowed ECi to apply nickel silicon carbide to its Titan engines for Experimentals. Once ECi was acquired, Continental gained access to its technical inventory and moved everything to Mobile.

Staff metallurgist Mike Byrnes explained that nickel and silicon carbide have strong, independent properties in cylinders when they’re applied with electroplating. Under his lab’s electron microscope, the combination resembles concrete with chunks of silicon carbide resting in nickel. The coating naturally retains oil that flows between the carbide, like water between rocks.

“The silicon, which is nearly diamond-hard, protects the nickel, and they work together to get a smooth surface that will allow an oil film to remain,” he said, adding that NiC3 cylinders also break in far easier than steel or chrome cylinders because all the wear is in the rings, not the super-hard NiC3-coated cylinder wall.

The industry-standard Knoop microhardness test for mechanical hardness confirms what Byrnes said. On that scale, diamond is 7,000, nickel silicon carbide is 3,300, hard chrome is 972, hardened steel is 822, and tooth enamel is 343.

Byrnes noted that pistons in many chainsaw and weed wacker engines are nickel plated since they run so rarely and would otherwise rust.

“When you get corrosion in a cylinder and start the engine, it’s like a cheese grater on your rings. You expose new, bare metals to rust again. With the nickel, you don’t have to worry about that, because the nickel protects the surface.”

Although the silicon carbide in Continental’s NiC3 is chemically identical to the grit in sandpaper, barrels feel smooth since the particles are only three microns in diameter and represent less than 5 percent of the mixture’s weight.

To electroplate a cylinder barrel, a powder of nickel and other chemicals is dissolved in water and stirred. A continuous, positive electrical charge is dispersed through the solution and the cylinder attracts the metallic salts that “plate out” the barrel. In addition to being harder, Byrnes believes nickel carbide adheres to the cylinder walls better than chrome. The process was invented in 1805 and is well-understood and highly refined, as I saw at Continental’s multi-acre plant near Mobile’s airport.

Plating adds about .008 of an inch to the barrel’s thickness. Half that is precisely removed when it is ground and honed by computer-controlled machines.

Bryon Denton, who is senior manager-engineering, joined Continental with the ECi acquisition. He said the production line for nickel-plating cylinders has been improved since they moved everything from San Antonio.

“Continental has implemented more quality controls and the chemistry is controlled to even higher tolerances than before,” he said. “That’s not to say ECi wasn’t diligent, but we’re doing more here and now have an on-site chemist. We’re a larger company with more resources, and this product line is growing.”

When I asked about the flakey chrome cylinders in my current engine, he said, “You get hard chrome circulating through an engine and it’s not a good thing.”

Denton added that with nickel silicon carbide, “Not only do pilots enjoy longer cylinder life, but if you don’t fly your plane a lot, it won’t rust up and ruin your rings and barrels.”

Less rust means more money for flying—and that’s always a good thing.

kevin knight is a 1,000-hour private pilot who splits his time and flying between humid Texas and humid Seattle.