Weather Membranes in High Corrosion Environments

Building in high corrosion zones, especially coastal or industrial environments, presents unique challenges. Salt, air, and moisture are a potent combination that can cause significant damage to buildings if not properly addressed. In this article, we explore which weather membranes are suitable for high corrosion or marine environments and dive into the science behind these materials. We’ll also examine how they protect structures while performing the necessary functions of a weather membrane. 

Why Corrosion is a Concern

High corrosion zones, such as coastal areas, have an aggressive combination of environmental factors: salty air, high humidity, and exposure to rain. Saltwater particles carried by wind can penetrate and cling to building materials, accelerating corrosion. Steel, metal frames, and other components are highly susceptible to rusting in these conditions, which can weaken the structure over time. Even without direct water exposure, moisture in the air combined with salt particles can infiltrate improperly protected areas, leading to material degradation. 

The role of a weather membrane in these environments goes beyond keeping rainwater out. It must also be vapor-permeable to allow moisture within the building to escape, preventing water from being trapped in the walls. In a high-corrosion environment, the membrane has the additional responsibility of blocking salty air and water from penetrating the building. The challenge is to ensure the membrane lets water vapor escape while keeping salt and liquid water at bay. 

Background:

The Science of Selective Permeability, TEEE (Non-Porous) vs. Microporous Membranes

When selecting a weather membrane, understanding the science behind how they work is essential. Two types of membranes are commonly used in moisture management: TEEE (Thermoplastic Elastomer Ether Ester) polymer membranes and microporous membranes. While both allow water vapor to pass through while blocking liquid water, they achieve this in different ways—critical distinctions for high-corrosion zones.

TEEE Polymer Membranes

TEEE polymer membranes are monolithic, meaning they are a solid, continuous material without visible pores. Despite their solid appearance, TEEE membranes allow water vapor to pass through due to their molecular structure. 

At the molecular level, the polymer chains in TEEE membranes are tightly packed, with tiny gaps between them. Water vapor molecules, being small and fast-moving, can squeeze through these microscopic spaces. However, liquid water molecules are much larger and cannot penetrate the barrier. The polar nature of water molecules creates surface tension, further preventing liquid water from passing through. 

This selective permeability allows water vapor to escape from inside the building while blocking external moisture and salt particles. The rate of diffusion is influenced by factors like membrane thickness, temperature, and the difference in water vapor concentration on either side, making TEEE membranes adaptable to different environmental conditions. 

Microporous Membranes

Microporous membranes, on the other hand, have tiny pores that allow water vapor to pass through while blocking liquid water. These pores are small enough that water molecules clump together and cannot pass through due to surface tension. However, individual water vapor molecules, which are much smaller, can diffuse through the pores. 

While effective in many situations, microporous membranes have a significant drawback: their pores can be compromised by substances that reduce surface tension, like oils or soaps. Once surface tension is broken, liquid water can pass through the pores, reducing the membrane’s effectiveness. 

Why TEEE Membranes Have the Edge in High-Corrosion Zones

Both TEEE and microporous membranes allow water vapor diffusion while blocking liquid water. However, TEEE membranes offer several advantages in high-corrosion environments: 

• Consistency: As a monolithic material, TEEE membranes provide a uniform barrier, reducing the risk of larger pores or defects allowing water through. 

• Durability: TEEE membranes are more resistant to physical damage, UV exposure, and wear over time. 

• Chemical Resistance: TEEE membranes are unaffected by substances that reduce surface tension, such as oils or chemicals, maintaining their water-blocking properties even in harsh conditions. 

• Long-Term Performance: Unlike microporous membranes, which can clog or degrade over time, TEEE membranes offer consistent performance and are easier to clean without damaging the material. 

Image Source: ProClima Article, What is TEEE? 

Strategies for Protecting your Structure in High-Corrosion Environments

If you can keep the structure airtight and watertight with a high-quality membrane, well detailed design, and proper installation, the risk of corrosion damage can be greatly reduced. 

Here are some effective strategies to consider: 

• Choose a non-porous yet vapor-permeable membrane like TEEE: This ensures that the membrane allows water vapor to escape but blocks liquid water and salt particles. An example of this is the ProClima Extasana Membrane. 
• Seal all membrane joints: Proper sealing with specialized tape ensures that no weak spots allow moisture or salty air to infiltrate. 
• Use a cladding system that has been weather-tested: Ensure the membrane and cladding work together as a system. For example, the AS4284 weather test ensures the integrity of the entire facade system. It also measures air leakage through the tested facade system, which is a critical element of keeping the salt out. 
• Specify weather-tested details around penetrations: Proper detailing around fixings and penetrations is crucial to prevent leaks. 
• Conduct on-site testing: Tests like the AAMA 501.2 rain wand test can verify the quality of the installation and ensure the membrane and cladding system performs as expected. 

Ensuring Long-Term Protection with the Right Membrane Choice

In high-corrosion environments where salt, water, and air can combine to wreak havoc on a building’s structure, selecting the right weather membrane is critical. While both TEEE and microporous membranes allow water vapor permeability, TEEE membranes offer clear advantages in terms of durability, chemical resistance, and salt protection. 

For projects in marine or high-corrosion zones, TEEE membranes provide superior long-term performance, ensuring your building remains protected against the elements while allowing necessary moisture to escape. This is why we have partnered with ProClima for our new Velo Facades product, which combines our state-of-the-art Click-on Cladding with their industry-leading TEEE weather membranes. ProClima’s tapes are the stickiest and longest-lasting on the market, providing the critical barrier needed to keep salt out of your building structure.