Why Low Copper Aluminium is Essential for Marine-Grade Lighting

What comes to mind when you think about coastal and marine environments?

Perhaps it's the salty spray of ocean waves, constant humidity, fluctuating temperatures, and constant moisture. These harsh conditions can take a serious toll on materials, especially lighting fixtures that aren’t designed to handle them.

As the following picture shows, corrosion is serious in marine lighting.

At first glance, common aluminium alloys might seem like a good option. But here’s the catch: many of them contain 2–6% copper. In a marine environment, that copper becomes a liability. It creates microscopic galvanic cells that accelerate internal corrosion, slowly weakening the fixture from the inside out.

So, what's a better alternative?

Low-copper aluminium alloys. These materials are specifically designed to resist the challenges of coastal and marine exposure.

In this blog, we’ll explore why low-copper aluminium alloys are a smarter choice for marine lighting and how to choose the right type for long-term performance in harsh environments.

Lighting in Harsh Marine Environments

Coastal areas pose serious challenges for lighting fixtures due to saltwater, high humidity, and strong weather conditions. Most floodlights use aluminium alloy housings, but salty air contains corrosive ions that quickly cause metal to oxidise and weaken.

Moisture and humidity speed up rust and corrosion, while UV rays from the sun and sudden temperature changes can break down materials and protective coatings. Over time, this leads to cracks, leaks, and other damage.

On top of that, waves and strong winds create vibrations and physical stress, which can wear out key components like brackets and seals.

Altogether, these conditions can rapidly damage lighting fixtures, leading to corrosion, electrical problems, and shorter lifespans without proper protection and materials.

How copper accelerates corrosion in marine aluminium

Aluminium is well-known for its natural resistance to corrosion. However, it is common in some alloys containing copper for added strength. This may become a drawback near the ocean.

In saltwater, which acts as a strong electrolyte, aluminium alloys containing copper are prone to galvanic corrosion. Copper is more "noble" than aluminium. This difference in electrochemical potential causes a corrosive reaction: the aluminium near copper-rich areas starts to corrode much faster, while the copper remains intact.

In effect, the copper causes the aluminium around it to break down, leading to pitting, material loss, and, over time, structural failure.

Why low-copper aluminium is ideal for marine lighting

Understanding the corrosive forces at play, the strategic decision to use low-copper aluminium for coastal areas becomes clear.

The primary benefit lies in minimising galvanic corrosion. By reducing copper content to very low levels, these alloys eliminate the electrochemical reaction that causes aluminium to corrode rapidly in saltwater.

Beyond corrosion, low copper alloys offer several other advantages. It’s easier to weld, which means manufacturers can build strong, smooth fixtures that can better handle impact and vibration. At the same time, low copper aluminium, especially those in the 5xxx and 6xxx series, offers a great balance of strength and lightness, making the fixture durable without adding unnecessary weight.

Key low-copper aluminium alloys for marine-grade lighting

Marine-grade doesn't just mean corrosion resistance. It also includes the durability to withstand harsh physical conditions such as wave impacts, salt spray, and heavy mechanical loads.

Among the different types of aluminium alloys, two groups are especially well-suited for use in coastal and marine areas. These are the 5xxx series, which are aluminium-magnesium alloys, and certain types from the 6xxx series, which combine aluminium with magnesium and silicon.

Here is a table for their main content and key features:

The 5xxx series is often seen as the best choice for marine use because of its excellent resistance to saltwater and its ability to be easily welded and formed into different shapes.

5052 offers a strong combination of corrosion resistance, strength, and formability, ideal for shaped or formed fixture housings. 5083 goes a step further, delivering superior strength and marine-grade corrosion resistance, making it well-suited for heavy-duty lighting installations exposed to the most demanding conditions.

The 6xxx series, particularly 6061, also plays an important role. This heat-treatable alloy provides a well-balanced combination of strength, corrosion resistance, and machinability. Although not as corrosion-resistant as the 5xxx series in submerged applications, 6061 is effective for atmospheric coastal exposure and structural components. Its low copper content, good thermal conductivity, and excellent weldability make it a versatile choice for exterior lighting systems, especially those requiring reliable heat dissipation during continuous operation.

At AGC, we deliver marine-grade lighting solutions designed for exceptional corrosion resistance and long-term durability. In addition to using low-copper aluminium for fixture housings, we ensure the reliability of every component, such as brackets treated with hot-dip galvanizing and screws made from high-grade 316 stainless steel. 

If you’re looking for lighting built for harsh marine environments, get in touch with us.