Stainless steel towel rails vs chrome: which will rust?

⚠️ Why a chrome towel rail can rust

A chrome towel rail can rust because the chrome is a thin plated layer and the tube underneath is usually mild steel. It can start in two places: on the outside, if water gets past the plating, and on the inside, if the water in the heating system isn’t treated.

We say “can” on purpose. It doesn’t mean every chrome rail will rust, and some chrome rails are plated brass rather than plated steel, which we come to further down. But if you’re wondering why the towel rail you’ve got now is rusting, these are the two ways it happens.

From the outside

Chrome is a finish, not the metal the rail is made from. The British Stainless Steel Association contrasts stainless steel with other steels, which suffer “general” corrosion, where large areas of the surface are affected. Ordinary steel rusts when water and oxygen reach it, and that’s the behaviour stainless steel is made to avoid.

So on the outside, a plated steel rail is only as good as its plating, and it lives in the dampest room in the house with wet towels hung over it most days. If water finds a way past the plating, there’s ordinary steel underneath. We can’t put a timescale on that and it isn’t inevitable, but it’s the mechanism behind a chrome rail that has started to rust.

It’s also why we’d look after the finish. Zehnder tells owners not to use abrasive or spray cleaners on any radiator, because they can have “a very damaging effect on the finish”. Zehnder is talking about radiator finishes in general there rather than chrome in particular. We’d take it more seriously on a plated steel rail, though, because the finish is also the rail’s protection.

This isn’t a new complaint. JIS Europe, which makes the all-stainless Sussex Range, says it was founded in 1997 “in response to the frustration of their chrome bathroom products rusting”.

From the inside

The inside of the rail is full of system water, the same water that goes round your boiler and radiators. If that water isn’t treated it can corrode steel from the inside, where you can’t see it.

Vogue UK says a sealed system should contain a BS 7593 corrosion inhibitor to maintain both the system and the towel warmer, and that going without “could result in corrosion or even failure”. Zehnder adds a practical consequence: “Failure to add an inhibitor can invalidate radiator warranties”. It also says the inhibitor should be topped up whenever the system has been drained down.

Building Regulations guidance in England asks for the same treatment when a new heating appliance goes in. Paragraph 8.8 of Approved Document L Volume 1 (2021 edition incorporating 2023 amendments) has the circuits cleaned and flushed, inhibitor added and the system commissioned to BS 7593. That paragraph applies to a new heating appliance rather than to changing a towel rail, but it’s the same standard the manufacturers are pointing to.

📍 Which circuit is your towel rail on?

Check the circuit before you think about which metal you prefer. A towel rail can be plumbed into one of two circuits, and on one of them Vogue UK won’t accept a rail with any steel parts, so the decision is made for you.

Vogue UK describes the two like this. An indirect or closed circuit is the sealed central heating loop, with the same water going round the boiler and radiators. Vogue says any towel warmer can go on it regardless of material, provided the system contains inhibitor. A direct or open circuit is different, because the domestic hot water that goes on to your taps and shower runs through the rail first. On that circuit, Vogue says, “only towel warmers manufactured totally from brass or stainless steel can be installed. Any model made from or consisting of ferrous metal (steel) components cannot be installed on a Direct/Open circuit.”

The reason is that the water is fresh mains water on its way to your taps, so nobody can dose it with inhibitor, and a mild steel rail would have new, untreated water running through it every day. So what decides which circuit you’re on is where the water ends up. If it comes out of a tap or shower, the rail is on the direct circuit, whatever your heating system is called.

JIS Europe says all of its models are 100% stainless steel and so suit “any plumbing system including open/hot water systems”. Zehnder describes its all-stainless Stellar Spa as “suitable for use with open heating systems”, but it doesn’t define that phrase as the tap-water circuit. If you want a Zehnder model on one, we’d have Zehnder or your fitter approve the exact circuit before ordering.

A common reason for choosing the hot water circuit is a warm rail in summer, when the heating is off. A dual fuel rail gets you that from the heating circuit instead. It has an electric element for the months when the central heating isn’t running, so the choice of material stays open. There’s more on it in the FAQs below.

Your fitter is the one who confirms which circuit you have. Vogue is clear about it: “Product compatibility is the responsibility of the installer.” If you’re replacing an existing rail or radiator, note which circuit it’s on while you’re working through your bathroom planning checklist, because the question needs answering before the order goes in.

🔥 What you give up with stainless steel or brass

What you give up is mostly money. Stainless steel and brass rails generally cost more than mild steel ones. How much more depends on the model, size and finish, so we’d price the actual rails you’re comparing rather than work from a rule of thumb.

On heat, the finish and the design decide more than the metal does. Vogue UK’s own figures give a useful illustration. At near-identical sizes, all at ΔT50 (the temperature difference the outputs are rated at), the mild steel Focus (MD001, 800 x 505mm) is listed at 252W in chrome and 420W in white. The stainless steel Kerve (MD036, 800 x 500mm) is listed at 243W, though Vogue doesn’t name the finish that figure is for. So the chrome mild steel rail and the stainless one are within a few watts of each other, and on the Focus the big jump comes from paint. Vogue explains that chrome plating reflects heat back into the rail, so a powder-coated version gives out more.

The same thing happens within a single stainless steel model. Zehnder’s Stellar Spa datasheet lists the 572 x 450mm size at 161W polished and 219W painted at ΔT50.

This isn’t a controlled test. The Focus has 14 bars and D-section uprights and the Kerve has 12 round bars, so don’t read it as one metal heating better than another. The practical point is that a shiny rail of any metal is a towel dryer first. If the rail has to heat the room, a painted finish or a larger rail matters more than what it’s made of.

For sizing, declared outputs and what ΔT50 means, see how to compare a bathroom radiator’s heat output. If the rail won’t heat the room on its own, underfloor heating is the usual partner.