Material selection

At the requirement, not the material. Each requirement names a property with a number, which a candidate either meets or does not.

As a filter: a candidate failing one is out however well it scores elsewhere. Mass, cost, availability and aesthetics then rank whatever survives.

Stiffness. Strength is the load before it breaks; stiffness is how little it bends before then. Section depth and shape affect stiffness at least as much as the material does.

The requirement, the property it demands, and the consequence for the user. A material name on its own earns nothing.

Texture, form and colour — each enhanced by a finishing technique after the material has been chosen on its properties.

Grip under a wet hand, hiding fingerprints, or preventing dirt being trapped — and it tells a user where to hold something with no instruction.

Anodising converts the surface of the metal itself so there is no coating to chip. Paint sits on top, and once chipped in a wet environment corrosion starts under its edge.

The colour goes right through, so a scratch shows the same colour beneath instead of a different substrate — the difference between looking worn and looking damaged.

Cost per part rather than per kilogram, including processing, waste and finishing — and over the whole product life, since a coating renewed twice is bought three times.

Available in the section and grade required, within the lead time, at a usable order quantity, and ideally from a second source so one supplier cannot stop production.

A product lasting fifteen years in a slightly worse material beats one lasting four in a better one, because the second is made and transported nearly four times over.

Essentials first — cost never buys back a failed property. Then whole-life cost, then what is genuinely available. Finally, state the trade-off you accepted and why.

The requirement from the specification, the property it demands, the evidence for that property, and the trade-off accepted. Missing the evidence link makes it a preference.

Secondary is published — property tables, standards, corrosion charts, supplier data sheets. Primary is your own testing on this material in this environment.

The supplier gains if you believe it and nobody independent checked it. It is evidence of what the material is offered as; a second source makes it a number you can defend.

Every choice gives something up. An answer listing only advantages reads as advocacy; naming the cost and arguing it was worth paying reads as judgement.