The chiller came back in a wooden crate. The client said 3 months, no cooling, compressor running but nothing cold. I opened it and the copper coil was green. Not that nice aged-patina green either. The kind of green that means something has been chewing through the metal.
That was a restaurant lobster tank. Saltwater, 24 hours a day, 68 degrees, and the coil lasted 90 days. I've seen worse. I've also seen copper coils in freshwater koi ponds going on year four with no issues. Same metal, different water, completely different outcome.
Here's what I've actually pulled out over the years, not what the brochures say:
| Material | Saltwater Outcome | Timeline |
|---|---|---|
| Copper | Pinhole leaks, green corrosion | 3-6 months |
| 90/10 CuNi | Pitting on the water side | 6-12 months |
| 316 stainless | Spotty pits near welds | 12-18 months |
| Titanium Grade 2 | No visible corrosion | 3+ years |
Copper conducts heat better than titanium. Nobody argues that. The issue isn't thermal performance. It's that saltwater has chloride ions, and flowing chloride water at 60-70 degrees erodes copper patina faster than it can reform. Once the bare metal is exposed, pitting starts. You don't see it until it leaks.
I used to think copper was fine for anything. A few years back I serviced a hotel display — freshwater, 200 gallons, copper chiller, running strong for 3 years. Then I took on that restaurant account and the coil was a sieve inside a quarter. I stopped recommending copper for saltwater after that. Not because I read a white paper. Because I had to mop lobster tank water off a loading dock.
316 stainless is the one that tricks people. It looks right. It's food-grade. It's cheaper than titanium. I pulled a 316 coil out of a customer's system after 14 months and the tube looked fine everywhere except along the weld bead. Tiny pinholes, right where the microstructure changes. Chloride finds the weak spots. Always does.
I said copper doesn't belong in saltwater. Freshwater koi ponds are a different story — copper works, it's cheaper, and I'm not going to tell a pond owner to pay titanium premium for water that doesn't eat metal. Different water, different answer.
Where titanium wins isn't on a spec sheet. It's on the service truck. I haven't pulled a titanium coil out for corrosion yet. I've pulled plenty of copper and stainless ones. The coil comes out, the compressor has been running with low refrigerant, and now you're looking at a compressor replacement on top of the coil. That's not a coil failure cost — that's a compressor failure cost.
I'm not going to tell you a titanium chiller lasts ten years. I don't know your water quality. I don't know your flow rate. I don't know if you clean the condenser once a quarter or once a year. What I do know is I haven't had to pull a titanium coil out for corrosion, and I've pulled enough of the others to know the difference.
When we spec a Ruibit seafood system, the chiller heat exchanger is titanium Grade 2. It's not because it's the fancy choice. It's because the alternative is a 6 a.m. phone call from a restaurant manager whose lobsters are dying and whose walk-in is full of warm water.
Last month I picked up a chiller from a diner. The customer had bought a cheaper unit because the titanium version was $300 more. It had been in service for 11 months. I put it on the bench and the coil had a pinhole the size of a pin, right near the weld. The customer wanted to know if it could be welded. I told him the whole coil would need replacing, and while we were at it, the compressor had been running low on refrigerant long enough that it was making noise.
He's buying titanium this time.
