Silicon Bronze:
Silicon bronze is a copper-based alloy containing silicon to increase strength and hardness. It combines toughness and durability, making it particularly useful for fasteners.
Our silicon bronze fasteners are manufactured from hard-drawn wire. The drawing process work-hardens the alloy, further increasing its strength and hardness.
Typical applications include boatbuilding, marine hardware, timber construction, electrical connections and architectural fittings. Silicon bronze screws, bolts, nuts and washers have a long history of use in wooden boats.
When new or polished, silicon bronze has a warm, reddish-gold colour. It naturally darkens with age to a rich brown, making it an attractive choice for traditional and antique-style bronze hardware. Because it is a solid alloy rather than a decorative coating, there is no plated finish to wear away.
Corrosion Resistance:
Silicon bronze has very good resistance to seawater corrosion. The Copper Development Association notes that silicon bronzes generally do not suffer pitting, a form of corrosion that creates small but potentially deep holes in the metal. This is a valuable advantage for marine fastenings, where maintaining strength over time is important.
Even 316 stainless steel, commonly called “marine grade”, can suffer pitting and crevice corrosion in seawater. Stainless steel relies on a thin protective surface film that needs access to oxygen to maintain and repair itself. Beneath fastener heads and inside joints, trapped water and restricted oxygen can allow corrosion to develop. The risk increases as water temperature rises, and damage can remain hidden from view. “Marine grade” should not be taken as assurance that a stainless steel fastener is suitable below the waterline.
Silicon bronze combines strength and toughness with dependable performance in seawater. These properties make it a well-established choice for boatbuilding and marine fastenings, above and below the waterline, when correctly specified and installed.
When choosing a fastener, also consider the materials it will touch and any chemicals it may encounter. See our Incompatible Materials guide for combinations to avoid.
Phosphor Bronze:
Phosphor bronze is a copper-based alloy containing tin and a small amount of phosphorus. These additions improve strength, corrosion resistance and wear resistance, making it useful in marine and industrial applications.
Its good wear resistance makes it particularly suited to bearings and bushes. Its spring properties and ability to withstand repeated loading also make it useful for springs and electrical contacts.
Phosphor bronze washers are compatible with silicon bronze fasteners.
Copper 5 - Cu Ni Si - Kuprodur
Kuprodur Cu5 (CuNi1.5Si) is a high-strength copper alloy containing nickel and silicon. It combines good electrical conductivity with wear and corrosion resistance.
Typical uses include electrical connections, specialist screws and nuts, overhead electrical line fittings, bearing bushes and valve guides.