Aquify Blog


Corrosion Prevention in Aquatics: How Aquify Goes Above & Beyond

September 01 2021



Corrosion is the nemesis of aquatic facility owners and operators everywhere. In addition to the corrosive effect of chlorine-based chemicals in pool water which can cause aquatic equipment like filters to corrode, corrosive air pollutants (e.g., chloramine vapor, trihalomethanes) in indoor pool environments can also wreak havoc on exposed metals. Plus, the humid, warm, and chlorine-dense atmospheric environment of the mechanical room promotes corrosion.

At Aquify, we take corrosion very seriously. We’ve implemented a comprehensive corrosion prevention system across all our products to mitigate corrosion risk in our regenerative media filters, strainers and baskets, and reducers, with each process working in parallel to create highly corrosion-resistant products specifically designed for the challenging aquatics environment.

Through a combination of careful material selection, meticulous manufacturing and welding procedures, cathodic protection, and an extremely durable powder coated finish, Aquify delivers best-in-class corrosion prevention across our entire product line.

Material selection impacts corrosion resistance

Fiberglass

The Aquify range of regenerative media filters is available with either a fiberglass vessel or a stainless steel tank. Used in critical applications like chemical manufacturing and marine design, fiberglass composites are designed to be non-reactive. Consequently, fiberglass aquatics products have been used by pool contractors and facility operators for decades.

Key in our composite design, Aquify employs a special corrosion layer as part of the fiberglass structure of the tank which is specifically designed to protect the integrity of the vessel. “We understand that there is wear that happens on these materials during the lifecycle of the equipment. Our corrosion liner is specifically designed to handle any degradation and protect the tank for its lifetime,” says Josh Kravitz, Product Engineer at Aquify.

Aquify strainers and reducers are also available in fiberglass.

Stainless Steel

In addition to fiberglass, we offer regenerative media filters with stainless steel tanks, in contrast to the carbon steel tanks that some other manufacturers use. Carbon steel tanks are coated with a polymer lining to prevent corrosion. “The issue with carbon steel tanks is that the liner becomes a single point of failure,” says Kravitz. “If the liner deteriorates, or is damaged in any way, the entire corrosion protection becomes compromised and, as a result, the structure of the vessel is left completely unprotected.”

Conversely, Aquify uses corrosion-resistant 304L stainless steel across its product line, with no liner required in the filter tank. The chromium in stainless steel reacts with oxygen to form a thin layer of chromium oxide on the surface of the steel. This passive layer prevents rust by acting as a barrier that limits oxygen and water access to the underlying metal surface.

For high-wear components like basket strainers that are under constant assault from debris, Aquify uses the more costly 316L stainless steel to ensure maximum corrosion protection. Due in part to the addition of the alloy molybdenum which helps fight off corrosion from chlorides, 316L stainless steel offers even greater corrosion protection than 304/304L stainless steel. The benefits of this alloy outweigh additional costs of a higher grade of material.

Stringent manufacturing process: the ace up our sleeve

Aquify’s comprehensive corrosion prevention strategy is anchored in our meticulous fabrication process:

Dedicated shop

We manufacture our stainless steel filters in a dedicated stainless steel manufacturing facility that has expertise, procedures, and practices specifically tailored to stainless steel. Plus, with a dedicated fabricator, the risk of cross-contamination with dissimilar metals (e.g., regular carbon steel) is eliminated, further reducing the risk of corrosion.

Aquify stainless steel reducers, tees, baskets and strainers are manufactured in an ISO-certified facility with extremely stringent manufacturing standards and protocols in place.

Correct weld procedures

Aquify follows precise weld procedures and best practices to ensure that vessels are fabricated correctly to maximize strength while minimizing the risk of corrosion. “Any weld that isn’t done correctly can be prone to corrosion so we’re meticulous about our welding practices,” says Paddy Ruzicka, Product Engineer at Aquify.

Passivation

stainless-steel-weld-passivation-process-at-aquify-systems-1

The properties of stainless steel that make it resistant to corrosion are present on the surface of the material. When stainless steel is heated to the point where it can be fused together (i.e., during welding), those protective properties are lost.

To ensure that the corrosion-resistant properties of the stainless steel are brought back to their native state at the weld point, Aquify implements an electrochemical weld cleaning system, a.k.a passivation. By passivating the weld, we regenerate the chromium layer on the surface of the stainless steel which acts as a barrier to the transfer of electrons, thereby mitigating oxidation and corrosion of the metal.

Weld testing

We test all our welds to measure how passive the area of the restored metal is. “Not only do we passivate the welds, but we’re able to measure the passivity to ensure that the optimal level has been attained,” notes Ruzicka. “We also conduct periodic non-destructive weld testing that involves x-ray imaging of the weld joints to verify the welding process and ensure the highest-quality end product.”

weld-xray-showing-lack-of-fusion
An example weld x-ray showing lack of fusion otherwise not visible to the naked eye.

 

Pickling

Aquify pickles its stainless steel aquatics products using a specialized acid solution. The pickling process promotes the regeneration of the passive layer on the surface of the stainless steel which acts as a barrier to oxidation.

“Pickling and passivating the tank are crucial steps to ensure corrosion protection that not every vendor takes. At Aquify, we’re very proud of the considerable time, effort, and specialized resources we deploy to ensure the integrity of our stainless steel products,” says Kravitz.

New non-metallic blast cleaning

sandblasted-stainless-steel-top-of-aquify-filter-1

Before powder coating stainless steel filter tanks, Aquify blasts the exterior with new (non-recycled), environmentally-friendly, abrasive blast media. We use this non-metallic blast media to accomplish two key objectives: first to remove any cross contamination that could have happened prior to fabrication, and second to achieve the correct surface profile prior to powder coating. "After blast cleaning we can be confident that the surface of the tank is not contaminated with any dissimilar, foreign metals which could promote corrosion, and proper adhesion can occur between the coating and substrate,” says Ruzicka.

Powder coating

After creating a pristine stainless-steel surface with the new non-metallic blast cleaning, the tanks are sent to a specialized powder coat facility to receive a corrosion-proofing powder finish. An electrostatic paint sprayer imparts a positive electric charge on the powder and accelerates it towards the surface of the tank through the electrostatic charge. The chemical bonding process strengthens the powder coating and, once cured, the bonds solidify to create an extremely durable physical barrier that prevents corrosion on the surface of the tank.

Sacrificial anode

Sacrificial anode before and afterAquify filters also offer a sacrificial anode as a final level of corrosion resistance, a process commonly used in critical applications (e.g., marine, underground piping). When a sacrificial anode and metal are placed in a corrosive solution, the anode effectively stops the corrosion of the stainless steel by sacrificing itself and corroding instead. “We consulted with a corrosion engineer to design our galvanic battery and recommend the optimal anode for our tanks,” notes Kravitz.

We’ve got your back

Corrosion is a fact of life in the world of aquatics and equipment manufacturers must take into consideration the entire aquatic ecosystem over which they have little control. “Everything in the aquatic environment is connected by water and this connection can transmit corrosion from one thing to another,” says Kravitz. “We take into account that other products in the system -- whether that’s a bolt on the waterslide or a pool ladder -- may be corroding, causing rusted steel flakes to pass through our filter, or creating stray currents that promote corrosion. Our products are designed to be able to resist corrosion, not only in a pristine indoor pool environment with perfect chlorination levels, but in a real-world setting with potential contamination and sub-optimal conditions.”

Aquify has deployed a comprehensive, multi-layered strategy that mitigates corrosion risk with no single point of failure. “It’s worthwhile noting that just because a product says it’s stainless steel doesn’t mean it’s corrosion-proof,” adds Kravitz. “At Aquify, we go the extra mile to perform all the necessary additional steps and measures to ensure our customers can feel confident in the quality and performance of our products over their entire lifespan. From our extensive material preparation and stringent fabrication process through to detailed installation and bonding instructions in our documentation, we’re committed to helping aquatic operators protect their equipment from corrosion.”

Get in touch to learn more about how Aquify can take your corrosion prevention to a new level with our comprehensive range of stainless steel and fiberglass aquatic products.

Topics: fiberglass, stainless-steel, process