How to Avoid Corrosion in Indoor Pool and Spa Environments

Corrosion in indoor pool and spa environments presents a unique challenge for architects and specifiers. The high-humidity, chlorinated air, combined with temperature fluctuations, creates a harsh environment that accelerates corrosion – even on materials typically considered corrosion-resistant. This blog will help you in understanding and mitigating corrosion risks in these environments, from design and material selection to maintenance strategies.

Why Indoor Pool Environments are Challenging

Indoor pools and spas create a unique set of conditions that can lead to rapid and severe corrosion. High humidity and chlorinated air vapor become trapped indoors, causing continuous exposure to chemicals that exacerbate corrosion. The worst-case combination of high moisture, chlorine, and fluctuating temperatures can corrode even the most resistant metals over time, potentially damaging structural integrity and aesthetic appeal.

What Causes Metals in Pool Environments to Corrode?

Corrosion occurs when metals react with oxygen, water, and other elements like chlorine in the air. In pool environments, the primary corrosion driver is the chlorinated water, which evaporates and disperses into the surrounding atmosphere, exposing metal surfaces to both moisture and corrosive chlorine. Here are the main types of corrosion architects and specifiers should be aware of:

1. Surface Corrosion: This is the most visible type of corrosion, where metal surfaces develop rust or discoloration. It often results from the direct contact of metal with chlorinated moisture in the air.
2. Galvanic Corrosion: Occurs when two dissimilar metals come into contact in the presence of a conductive solution (like chlorinated water). This type of corrosion can be severe, especially when incompatible metals are used together in pool fixtures.
3. Crevice Corrosion: Found in confined spaces where chlorinated water can become trapped, such as under bolts or in crevices between joined materials. Over time, trapped moisture in these areas can create high-chloride concentrations, accelerating corrosion.

Strategies to Overcome Corrosion in Pool and Spa Environments

Addressing corrosion early in the design phase is essential to avoid costly fixes down the line. Here are strategies architects and specifiers can use to minimize corrosion risks:

1. Material and Coating Choices
   Choosing the right materials and coatings is critical. Stainless steel, particularly grades such as 316 or duplex stainless steels, offers higher resistance to chloride-induced corrosion. Coatings like epoxy and powder coatings can add an additional barrier, but it’s important to verify the compatibility of coatings in high-humidity, chlorinated environments.
2. Installation Strategies
   Designing with corrosion in mind involves planning for dissimilar metals to avoid galvanic corrosion. This includes separating metals using non-conductive materials like rubber gaskets, plastic washers, or other isolators. Additionally, ensure that bolts, fasteners, and joints are made from the same or compatible materials to reduce risk.
3. Ventilation Systems and Dehumidification
   Proper ventilation and dehumidification play a major role in controlling humidity levels and removing chlorinated air. Effective HVAC systems reduce the time metals spend in contact with corrosive air, significantly extending their lifespan. Architects should work closely with HVAC specialists to design a system that meets the high demands of indoor pool environments.
4. Maintenance and Cleaning
   Regular maintenance and cleaning reduce the accumulation of corrosive chemicals on metal surfaces. A maintenance plan for cleaning metal surfaces with fresh water, checking for early signs of corrosion, and treating affected areas can mitigate surface and crevice corrosion before it spreads.
5. Sacrificial Anodes
   Sacrificial anodes, often made from zinc or aluminum, are installed to protect other metal structures. They attract the corrosion process away from more important components, effectively “sacrificing” themselves to prolong the lifespan of the primary structures.

Indoor pool environments are challenging, but understanding corrosion risks and implementing these strategies can make a big difference. Early planning and material selection can prevent corrosion problems, extending the life and durability of your designs.