Repair and refinishing solutions for fibreglass pools

by arslan_ahmed | October 27, 2023 11:00 am

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By Peter Gibson

The first fibreglass/polyester resin boat was built in 1942 by Ray Greene of Toledo, Ohio. It was built using Owens Corning fibreglass fabric and American Cyanamid resin. The first rudimentary glass fibres were produced in 1932, and polyester resin in 1942. These early glass fibres and polyester resin formed the basis for the composites industry.

Today, the composites industry is extraordinarily complex, with many unique fabrication techniques, resin systems and reinforcements. Until that time, legacy materials such as steel, wood, and concrete were the chief building materials for most endeavours. As fibreglass boat building got more popular in the 1950s, an idea was hatched to build a pool out of fibreglass; and thus, the fibreglass pool industry was born. Fibreglass offers strength, is light weight, and low maintenance.

The same basic fabrication materials used for boats were utilized. Initially, there was much skepticism about this “new” material called fibreglass, because at the time, concrete dominated pool construction. The same reluctance held true for boats in the transition from wood to fibreglass. In addition, the pool installation techniques were not refined, leading to problems.

Addressing the cobalt problem

Until the 1980s, there was a lull in the installation of fibreglass pools because of perception and a lack of marketing. Also, during this period, there was a major problem with cobalt (black) spots on the surface originating from blistering, and pools that were not set correctly caused problems, and some bowed inward.

Towards the end of the 1990s, there was significant improvement with respect to installation techniques and fabrication materials. Fabricators were searching for ways to eliminate the blistering (cobalt) problem.

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The mechanism of cobalt spot development

The resins utilized are not 100 per cent impervious to moisture ingression. Many epoxy resins are more moisture resistant. During the fabrication process, microscopic voids in the resin create cavities that water molecules migrate into, together with water soluble materials such as the cobalt promotor. The cobalt in the resin is part of the curing system; it is an activator that is added to the resin which reacts with the catalyst to start the curing reaction. These resins do not cure like epoxies. Free radicals are involved in the curing process with these types of resins. These micro fluids build up pressure in these cavities and eventually burst, spilling their contents on to the surface, which is then oxidized by chlorine. This forms the unsightly purplish cobalt oxide. The cobalt in the resin is the promotor that reacts with the initiator to produce free radicals that start the polymerization process. It is an essential activator for resin curing. Before the use of cobalt, the resin was not room temperature cured and had to be post cured.

The incorporation of bisphenol A (BPA) epoxy vinyl ester resin (EVER) into the fabrication process has all but eliminated the cobalt issue. Today, most reputable pool fabricators utilize EVER in their fabrication schedule as it is more water resistant. The late 1990s also saw the development of new finishes that included “shimmery” looks from the inclusion of thermoplastic particles/flakes in clear resin, which was laid down first before the colour coat and lamination. The initial problem was the haziness of that finish. Today, most fibreglass pool manufacturers offer the shimmer look and solid colours.

Repairing and resurfacing

As the fibreglass pool population has aged, many old pools have come online for refinishing. The most common problems are:

• Cracks in the structure due to movement of the pool or improper setting. Most cracks can be repaired by placing a fibreglass mat first over the cracks.
• Bowed walls. When the pool is not set correctly using faulty techniques, the pressure exerted by dirt puts pressure on the walls causing them to “bow” inwards, leading to bowed walls. One solution would be to cut out the affected area and pump in gunite to create a firm foundation for fibreglass lamination to that area.
• Deterioration of the gel coat finish. All old fibreglass pools show some degree of gel coat deterioration. This can manifest in two ways: thinning of the gel coat that exposes the fibreglass structure and chalkiness.

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What is chalking?

Chalk is a white powdery substance found on coatings and gel coat. The resin binder eventually breaks down due to ultraviolet (UV) exposure and exposes the pigment. The powdery substance is the breakdown product of the pigment.

What is a gel coat?

A gel coat is a specialized resin that imparts colour to fabricated products. It contains UV additives, pigments, activators, and rheological chemicals to control the resin flow on a vertical surface. They have a much higher viscosity than laminating resins and is the first resin applied to the mould.

The fibreglass structure should be properly prepared to receive the chosen coating. Lightly sand the pool to remove any surface contaminants and clean it thoroughly. There is no need to remove the old gel coat. Be sure to use a compatible primer with the coating selection. For pools with a lot of blisters, sand the blisters and dehydrate the fibreglass.

Coating choices

• Two-part epoxies with a short service life.
• 100 per cent solids, zero volatile organic compounds (VOCs) novolac epoxies.
• Polymer composite resins incorporating BPA EVER for a long service life. This will eliminate blistering and repeated resurfacing.
• Modified isophthalic neopentyl glycol (ISO/NPG) gel coats for long service life.

The purpose of these coatings is to improve the esthetic appeal of old fibreglass pools, and to protect the underlying laminate or pool structure. Once the gel coat wears away, the pools lose the uniformity of appearance and look dull and uninviting.

The coatings mentioned are the main options available, because in the coatings industry, very few coatings perform well in pools, hence the limitation in options. It is recommended to use only performance coatings for pool resurfacing, because if not, it will certainly deteriorate fast, and lead to rework.

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Thermal spray pool finishes

This system utilizes a thermoplastic powder that is pneumatically forced into a very hot flame that melts the plastic powder, which then flows on the surface as liquid to form a thermoplastic coating once the heat is removed. There is no chemical cure or initiator utilization, meaning it is subject to embrittlement over time.

This new product was introduced to the pool industry more than five years ago. Unfortunately, it was overhyped and sold on unsubstantiated/exaggerated claims. It was offered as a product suitable for concrete use, but it never worked, resulting in all those applications failing, requiring expensive rework. In addition, it is only 6-mils thick and offers limited-service life.

In contrast, performance thermosetting resins are applied ± 80-mils thick. All legitimate products in the coatings industry are based on thermosetting not thermoplastic resins. Some pool professionals still use it on fibreglass pools, but after a few years in use, a deterioration has now come to light.

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Many pool professionals signed up for the training program, but now have abandoned the material for more reliability. To avoid rework, high-performance epoxies, polymer composite resins, and modified gel coats offer the longest service life and peace of mind for contractors. It is best to avoid unproven coatings. In fact, the coatings industry is notorious for exaggerating product benefits, so it is imperative to proceed with caution when selecting a coating.

To this day, thermal spray coatings have not been recognized as a legitimate product in the pool industry as there are no written specifications and endorsements by aquatic consultants. A big problem in the pool industry remains the lack of body of knowledge for pool professionals to draw from, especially regarding polymeric materials, which could allow them to make a coating selection based on accurate information. It is easy for a manufacturer to make claims about their product.

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Fibreglass tank story

The fibreglass tank under review holds very aggressive industrial chemicals. The same fibre-reinforced plastic (FRP) (e.g. BPA EVER) materials used to rehabilitate fibreglass pools are the same ones used to restore industrial fibreglass tanks that hold very corrosive chemicals.

If the FRP materials can hold up in tanks, then the pool water is very low on the corrosive spectrum. Pool water has a pH 7.2 to 7.6. These materials can contain the full range of the pH scale. For a very long service life, FRP materials have proven to outperform most coatings used in immersion service. Pool chemicals are far less hostile to fibreglass than corrosive industrial chemicals.

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Conclusion

As with all products, there comes a time when a fibreglass pool requires repair and resurfacing. Today, these pools command about 10 per cent of the pool population because of their inherent benefits compared to concrete.

Modern fabrication methods and materials will extend the life of fibreglass pools, but the older ones will require refinishing at some stage. As pool professionals embark on their resurfacing projects, they should remember to choose some candidate coatings, and then assess which one will get the job done for long term service.

 Author

Peter Gibson is president of GRC Fiberglass Coatings. Over the past 30 years, he developed fibreglass coatings and linings specifically for fibreglass and concrete pools. Gibson also offers training in the use of these products through the certified applicator training course. He is available to answer all technical questions to resurface concrete and fibreglass pools. Gibson can be reached at resinmaster@gmail.com.

Source URL: https://www.poolspamarketing.com/trade/features/repair-and-refinishing-solutions-for-fibreglass-pools/

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