May 7 2025
You could, as we would say in the old country, of knocked me down wiv a fevver.
The F-35 Joint Program Office released a statement about a previously (almost) unreported problem.
This is not the JPO’s pattern. More often, the bad news emerges in a Government Accountability Office or Director of Operational Test & Evaluation report, or is elicited by specific questions in testimony. I’m not sure what prompted this discussion of corrosion and surface grime. I suspect that there may be incoming from GAO.
But the latest statement is in accordance with the JPO’s usual practice when it comes to presenting bad news, in adopting the same narrative arc as the American folktale No News or That’s What Killed The Dog (if you’re French, Madame la Marquise): a story that begins with a minor tragedy and proceeds to unfold in ever more gruesome detail with worse news at every stage. Let’s begin with Fido RIP.
“A Misconception of Corrosion”, it begins, to put any critics on the back foot. An F-35’s “sleek lines” are “slightly marred by streaks of discoloration. Exposure to jet blast, airborne debris, oil, and fuel residues.. has left marks on its surface — a common occurrence for any fighter aircraft. But beneath that worn exterior, low observable (LO) characteristics remain uncompromised.”
The JPO goes on to explain that this is not dirt but “coating discoloration”, a change in the complex and classified surface material that is applied to the aircraft to maintain its stealth characteristics. It’s probably accurate to say that shaping is the first line of defense in stealth, followed by radar-absorbent structures and materials built into its edges. But those still leave a “fuzzball” of radar scattering: coatings and tight tolerances suppress that by ensuring that surface RF currents flow smoothly. The discoloration marks “do not indicate a loss of coating integrity nor stealth performance.”
There seems to be a little more of that going on. As F-35s get photographed in the wild, there are observable differences in plumage…
On the left, “off to the champagne gala reception”; on the right. “Tuesday afternoon out-of-oregano dash to Tesco”.
But OK, it’s not a problem, except there is a program to fix it. JPO “has developed and introduced a new aircraft coating designed to significantly reduce or eliminate discoloration, enhance durability, and extend the coating’s service life. Over the coming years, this new coating will be applied to fielded aircraft as part of routine maintenance.” This will not be Home Depot paint. It will not even be the paint that the Home Depot salesperson upsells you to, after observing that their regular grades of paint are rubbish, and likely toxic.
Still, just a coating – but where in tarnation did my dog git that burned horseflesh?
Welcome to the C word. Corrosion. Further down the page than all too many people will read: “The F-35’s complex airframe, made from a blend of aluminum, titanium, and carbon composites… introduces the risk of galvanic corrosion when these dissimilar metals interact in humid, salty environments.” But now, JPO “has made corrosion control a top priority, supported by a coordinated enterprise-wide strategy.”
But then comes the kicker: “For several years, the F-35 JPO operated without a fully developed corrosion management framework. This left field maintainers and depot crews playing ‘catch-up’ as the fleet matured.”
There were candles in mah house?
First of all, there clearly wasn’t a corrosion management program at one time, that was stopped. “Several years” means “forever” or for about 25 years.
This should not have been the case, because GAO sounded the alarm in December 2010, based on the major corrosion problems encountered by the F-22 as the fleet expanded beyond the Mojave Desert. But back then, the F-35 program was in deep snot in all directions (eight months after the program director got fired, and as the new leadership was having trouble even re-establishing a schedule). Like so many other issues, it was pencil-whipped into compliance and everyone hoped for the best.
A second warning flare went off in 2017, as the Royal Australian Air Force started introducing the F-35 to RAAF Williamtown, a couple of miles from the Pacific. Consultants KPMG were commissioned to study different anti-corrosion strategies. A redacted version of the report was released, and fingered a specific problem: a new lightweight aluminum alloy, Alcoa 7085, had been adopted for the F-35 after the near-catastrophic weight overruns of 2003-04, and it was unexpectedly susceptible to intergranular corrosion – the bad kind of corrosion, not the self-inhibiting surface corrosion that is characteristic of aluminum.
Of course, the contractor weighed into the discussion with its customary candor.
As a fifth generation aircraft, the F-35 is the perfect blend of all-aspect stealth even when armed, low-probability-of-intercept radar, high-performance air frames, advanced avionics and highly integrated computer systems bringing an unrivalled, gods-eye view of the battlespace. However, as with any new and highly complex technology, the aircraft have suffered some delays and experienced lessons learned with some of the technological innovations that will make the aircraft the dominant fighter aircraft of the 21st century.
As identified recently, a small number of earlier batch aircraft were discovered to have a small amount of corrosion…
That soothing tone is all too familiar.
There is nothing to be said positively for corrosion. It’s the silent killer of structures. Even the JPO statement says “it works quietly and gradually, often concealed beneath coatings or hidden within seams, joints, and fasteners”. In most cases, the best or even only way to fix it is to prevent it from starting, which is why you will find the bilge areas of commercial aircraft primed, coated, and wet-assembled with sealants in place.
Galvanic corrosion, which can occur when two dissimilar alloys are in contact and exposed to water, is particularly no fun at all. It doesn’t have to be salt water: the H2O is an electrolyte. The two metals act as a battery, and one result can resemble the kind of corroded metal found in a leaky battery. In the case of the F-22, another contributing factor was the lack of drain holes, which are bad for stealth; this allowed water to accumulate in hard-to-inspect corners of the airframe. (This type of corrosion seems to sneak up on people, although it’s been encountered in aviation for almost 100 years: the pioneer pilot and sailor Sir Francis Chichester suffered from water leaks in the floats of his de Havilland Gipsy Moth because a previous owner had replaced the bottoms of the aluminum floats with steel.)
The question at this point is how much damage has been done and how much it will cost to fix, since by now there are many aircraft in the fleet that have been serving for ten years with inadequate corrosion management.
Well, suh, some people say that it was the shock of your wife running away with the chauffeur… but other than that, they ain’t no news.
(Updated May 9 with more details on galvanic corrosion)