What damage should you inspect on an engine that has been in storage? Corrosion is the main concern.

When an engine sits in storage, the real trouble isn’t always obvious from the outside. You might expect to find leaks or worn components, but the thing that deserves the most attention is corrosion damage. In the world of powerplant maintenance, corrosion can creep into places you can’t see until you pull the covers off and start inspecting with a few careful eyes. And yes, in a Jeppesen Powerplant context, that’s a key takeaway: corrosion is the damage type you want to verify first when an engine has been idle for a while.

Why corrosion matters more than you’d think

Think of metal in a damp closet. It doesn’t rust overnight, but over weeks or months, moisture and oxygen quietly team up to attack. Engines are full of metal—steel, aluminum, titanium alloys, copper alloys in bearings and bushings, and lots of fasteners. In storage, those materials become sitting targets for corrosion, especially if humidity is high or condensate forms in hidden cavities. When corrosion gets underway, it can thin walls, pit bearing surfaces, or corrode valve seats and seals. The result? A compromised engine once you try to bring it back to life.

Corrosion is sneakier than it looks. The engine may appear clean on the outside while corrosion has taken up residence in less accessible corners—inside water jackets, oil passages, or behind protective shrouds. That’s why you don’t rely on a quick surface wipe. You need to check both what you can see and what you can’t easily see.

Where corrosion loves to hide

• Inside the cylinder head and along valve seats. Corrosion can form pits that disrupt sealing or heat transfer.

• On crankshaft journals and bearing surfaces. Even a few micro-pits can affect oil film integrity.

• In oil and coolant passages. If water finds its way into lubricants or coolants, corrosion can grow where you’d least expect it.

• Around fasteners and threaded holes. Corrosion can weaken bolts or studs, leading to loosening or galling.

• In hidden cavities and around gaskets. Gaps around seals can trap moisture and promote rust where you won’t notice it at a glance.

Let me explain it this way: everything that isn’t perfectly dry and clean has a chance to gather a little rust or corrosion over time. And when you’re dealing with an engine that’s been idle, even a tiny deterioration can become a big deal once you start it up again.

A practical inspection plan you can actually use

Here’s how to approach an engine that’s been in storage, with corrosion as the star of the show.

1. Start with a thorough visual survey

• Look for any reddish or brownish staining on exposed metal surfaces, especially around flanges, housings, and fastener patterns.

• Inspect paint for bubbles or blistering. Sometimes you’ll see tiny rust specks under coatings that looked fine from the outside.

• Check for signs of moisture intrusion on seals and gaskets; warped or swollen gaskets can be a telltale clue.

2. Dig a little deeper with internal checks

• Use a borescope to peek into the combustion chamber, valve area, and intake/exhaust passages. Do you notice any roughness, pitting, or oxide specks that shouldn’t be there?

• Examine oil passages and the oil reservoir for sludge or discoloration that might indicate water or moisture mixing in.

• If you’ve got access to fuel, sample it for water or particulates. Fuel contamination often accompanies storage problems, and water in fuel is a common corrosion accelerant when it makes its way into metal surfaces.

3. Assess critical surfaces

• Inspect cylinder walls and piston rings for pitting or discoloration. Small pits can grow if left unchecked.

• Check crankshaft journals and bearing races for corrosion-related wear. Look for dullness or micro-pitting that might spoil bearing performance.

• Look at valve stems, seats, and guides. Any corrosion here can derail sealing and performance.

4. Consider moisture indicators and environmental history

• If the storage site was humid, note how long the engine rested there and what measures were taken to control humidity.

• Check moisture indicators or desiccants that were used in the crate or storage area, and review whether they were replaced or regenerated on schedule.

5. Decide on a course of action, not just a verdict

• If corrosion is localized and mild, you might plan cleaning, passivation, or coating where appropriate, then re-evaluate.

• If you find deep pits, galling, or loss of material on critical surfaces, replacement of parts or more extensive overhauls may be warranted.

• Always document findings and communicate what you recommend before returning the engine to service.

Corrosion vs. other damage types: where storage shifts the risk

• Electrical system failures: these can show up after storage, especially if moisture somehow finds its way into wiring or connectors. But electrical issues often surface later as the system cycles through power-up sequences.

• Fuel contamination: water in fuel is a storage-related risk, yes, but it’s more a driver for the fuel system than a stand-alone surface problem. It can aggravate corrosion if moisture travels with the fuel.

• Mechanical wear: you’ll see wear after use, but during storage, the big concern is the environment—rust and corrosion creeping into metal surfaces that aren’t moving much.

So, when you’re evaluating a stored engine, corrosion isn’t just one item on a checklist. It’s the primary lens through which you should view the whole return-to-service process. It sets the tone for rest of the inspection, helps prioritize what to fix first, and can save you from surprises after you bring the engine back online.

A few practical tips you’ll actually use

• Control the storage environment. If you can, keep humidity low and temperature stable. Desiccants and humidity-controlled storage are worth their weight in gold.

• Use corrosion-inhibiting coatings or treatments where recommended by the OEM. They can slow down corrosive processes in areas that are hard to seal off.

• Rotate or cycle components periodically if storage is prolonged. Even a small amount of movement can help prevent moisture from settling in critical pockets.

• Keep a running log of inspection findings, corrosion levels, and any parts replaced. This isn’t just about the present—it helps with future storage scenarios too.

• Don’t skip the hidden corners. A good inspection plan targets both visible and concealed areas. The best corrosion checks feel like detective work, not a quick glance in a bright light.

A quick mental checklist you can keep handy

• External surfaces: rust stains, coating integrity, fastener condition.

• Accessory housings and mounting surfaces: corrosion signs around bolts and flange faces.

• Internal passages: borescope-check of cylinders, valve seats, cooling and oil channels for corrosion deposits.

• Fluid samples: oil and fuel for water and particulates.

• Historical storage data: humidity levels, desiccant status, storage duration.

The human side of returning an engine to service

There’s a real satisfaction in seeing an engine go from “stored and uncertain” to “ready for life” again. It’s not just a technical win—it’s a confidence regain for the crew and the operator. The moment you spot corrosion early and fix it, you’re reducing the chance of a downstream failure. You’re buying reliability, safety, and peace of mind. And that matters when you’re miles from the nearest shop and the weather is turning.

Final thoughts: the one true north for stored engines

Corrosion damage is the pro‑active, practical focus when engines have parked for a while. It’s not the flashiest topic, but it’s the one that keeps engines honest after time off the ramp. By combining careful visual checks, targeted internal inspections, and sensible storage best practices, you minimize surprises and maximize the chance of a smooth, safe return to service.

If you’re brushing up on Jeppesen Powerplant fundamentals or comparing notes with peers, remember this: corrosion isn’t just a problem to fix, it’s a signal. It tells you where attention is needed, what to replace, and how to set up future storage so the next startup isn’t haunted by rust or pitting. And when you approach it with curiosity, patience, and a clear plan, the whole process becomes less daunting and a lot more manageable.

So next time you’re faced with an engine that’s spent time resting, start your investigation with the question that really matters: where has corrosion taken hold, and how can I address it before I bring the engine back to life? The answer isn’t just about preventing a failure—it’s about delivering reliable performance when it counts, and that’s something every powerplant professional can stand behind.