When it comes to marine fabrication on the BC coast, the material debate is essentially settled: aluminum wins for almost every application. While steel still has its place in certain marine contexts, the weight, corrosion, and maintenance advantages of aluminum make it the default choice for docks, floats, platforms, and marine infrastructure. Here is the detailed comparison.
Weight: The Decisive Advantage
Aluminum weighs roughly one-third as much as steel. For marine structures, this translates directly to greater buoyancy and freeboard with smaller flotation systems, lower transportation costs from fabrication shop to installation site, easier handling during installation and maintenance, reduced loading on mooring systems and anchors, and the ability to build larger platforms on the same flotation. For float systems, this weight advantage is transformative — you can build a larger, more capable platform for the same flotation investment.
Corrosion Resistance
Marine-grade aluminum alloys (5086, 5083, 6061-T6) naturally form a protective oxide layer that resists saltwater corrosion. Steel, even galvanized steel, will eventually corrode in constant saltwater exposure. The maintenance difference is significant: aluminum structures may need cleaning and occasional anodizing touch-up, while steel structures require ongoing painting, coating, and rust treatment. Over a 20-year service life, the maintenance savings alone can offset aluminum's higher initial cost.
Structural Performance
While steel is stronger per unit area, aluminum's strength-to-weight ratio is competitive for marine applications. Marine aluminum structures use larger cross-sections than equivalent steel structures, but the total weight is still dramatically lower. For dynamic marine environments where wave loading and vibration are constant, aluminum's fatigue resistance and ductility are advantages.
When Steel Still Makes Sense in Marine
Steel is still preferred for some marine applications: heavy mooring hardware subjected to extreme point loads, wear surfaces on fender systems where abrasion is the primary concern, below-waterline structures where cathodic protection is well-managed, and budget-constrained projects where a shorter service life is acceptable.
For marine fabrication projects on Vancouver Island, T & C Fabrication recommends and works with marine-grade aluminum as the default. Call Ted at 250-202-1643 to discuss your marine project.
