Metals in a house tarnish, corrode or stay put, and it is worth knowing which

This is written to be used rather than admired. Each section below is a decision about metal fittings, and each one has a default.

Tarnish is not corrosion

Brass and copper form a surface layer as they react with air and skin oils, which darkens and colours them without weakening the metal. Iron and ordinary steel corrode, which consumes the metal and continues inward if left in damp conditions.

The first is a finish changing and the second is a material failing, and they are frequently described with the same word. This is why unlacquered brass handles that look dark after five years are fine, and why a rusting steel bracket in a shower is not.

Lacquer decides whether it ages evenly

A lacquered brass fitting stays bright until the lacquer wears through at the point of most contact, after which that patch tarnishes and the rest does not. The result is a blotch rather than a patina, and stripping the remaining lacquer is usually the only way to recover it.

Room to room, unlacquered or living finishes darken everywhere and lighten where hands touch them, which produces the uneven-but-coherent look people actually want. Choosing between them is really choosing between low maintenance now and a good appearance in ten years.

Stainless steel is a family, not a material

The common domestic grade resists corrosion well indoors and can still pit in salty or chlorinated conditions. A marine grade with added molybdenum resists that considerably better, and is what specification for coastal locations and swimming pools calls for.

In practice, tea staining — brown speckling on outdoor stainless near the sea — is this failure and is usually a grade choice rather than a cleaning failure. Cleaning stainless with steel wool embeds iron particles that then rust on the surface, which is a common self-inflicted problem.

Two metals plus water is a problem

When dissimilar metals are in contact in the presence of moisture, one corrodes preferentially, which is why an aluminium component fixed with the wrong screw fails first. This shows up in gutters, external fixings, radiator systems and anywhere plumbing joins different materials. Using the fixings specified for the material, rather than whatever is in the tin, is the practical version of the rule.

In heating systems, mixing metals without appropriate inhibitor is a known cause of sludge and radiator failure, and is a job for a heating engineer.

Finishes on top of metal

Powder coating, anodising, plating and painting are all layers on a substrate, and they fail at edges, at fixing holes and where they were damaged in transit. A chip in a plated tap exposes the base metal and corrosion then spreads under the plating from that point. Solid brass or solid stainless components cost more and have no layer to breach, which is why they are specified in demanding positions.

Over years, asking whether an item is solid or plated is a short question that predicts most of its long-term appearance.

Mixing metals in a room

Matching every metal in a kitchen or bathroom produces a coordinated look that reads as a showroom and dates as a set. Two metals, used consistently — for example one for ironmongery and one for lighting — reads as considered rather than accidental. Warm metals sit better with warm timber and cool metals with grey stone, which is a more reliable guide than any rule about matching.

The exception is fittings that touch each other, where a mismatch reads as an error rather than a choice.

The takeaway

Buy solid rather than plated where hands touch it, and decide whether you want a metal that changes or one that does not.

A room that is used will always beat a room that is finished.