Dealer says European cars always need new discs with every pad change because the metal is softer — is that true?

The coastal detail in your question is worth addressing because it produces a real and harmless symptom that gets used to sell parts.

Discs rust quickly in damp salty air — surface rust appears within a day of rain and looks alarming. It is removed by the pads within a few hundred metres of driving and means nothing. Rust on the friction surface of a disc that is driven regularly is not a defect.

What coastal air genuinely does affect is the parts around the brakes: caliper slide pins seizing, corroded pad hardware, and rusted hubs making discs hard to remove. Those are worth attention at a pad change and they are cheap to sort while everything is apart.

So there may well be a good coastal-climate recommendation available. It is not the one you were given.

The softer-metal explanation is nonsense as stated. Disc material varies between manufacturers and applications, and it does not sort neatly by continent, and "softer metal" is not a reason a disc would need replacing at one pad change rather than two.

A disc will normally outlast two or three sets of pads, sometimes more, depending on driving and on the pad compound. Replacing them at every pad change is not a rule anywhere.

What genuinely justifies replacement is measurable rather than rhetorical:

• Thickness below the minimum. Every disc has a minimum thickness cast or stamped on it. Measuring with a micrometer takes a minute and is the definitive answer.
• Excessive lateral runout or thickness variation, which cause pulsing under braking. Also measured, not guessed.
• Deep scoring, cracking, or heat damage.
• A lip at the outer edge deep enough that new pads will not seat properly.

Ask for the measured thickness and the manufacturer's minimum. A workshop that has actually inspected them can give you both numbers immediately.

There is a legitimate version of the argument that gets mangled into what you were told, and it is worth knowing so you can tell them apart.

Some manufacturers do specify replacing discs at every pad change, for their own vehicles, in their own service documentation. Where that is genuinely in the manufacturer's schedule, a franchised workshop following it is not inventing anything.

The difference is that this is a model-specific instruction, not a property of European cars in general, and it can be checked. So the right question is: "is that in the manufacturer's schedule for this vehicle, and can you show me?"

If the answer is yes, you can decide whether to follow it. If the answer becomes vague, you have learned something about the recommendation.

Practically: ask for the measurements, and if you are not satisfied, get a second opinion from an independent workshop. Brakes are a competitive job and a measurement is quick.

And if the discs do turn out to be near minimum at 49,000 km, that is itself worth asking about — it would suggest something unusual, like a caliper that has been dragging, and replacing the discs without finding that would mean doing it again in two years.