Addressing Chloride Ion Corrosion with HJ3's CarbonSeal System
Chloride ion corrosion is a formidable environmental challenge, commonly encountered in marine environments, significantly contributing to the corrosion of steel and other metals. This menace extends its presence beyond marine settings and is also prevalent in humid conditions. For example, it can occur when water from humid air, laden with soluble chloride salts, condenses. The corrosion wrought by chloride ions is often termed 'pitting corrosion' due to its localized nature, resulting in small pinholes within metal structures. Moreover, when steel serves as reinforcement for concrete, chloride corrosion becomes a concern.
In fact, the exposure of reinforced concrete to chloride ions stands as the primary cause of premature corrosion of the steel reinforcement. Concrete typically offers corrosion protection to steel due to its alkaline environment, boasting a pH range of 12 to 13. In this environment, a thin oxide layer, or passivating layer, forms around the steel, shielding it from metal atom dissolution. However, if this passive oxide layer is fully eroded, typically when the concrete's pH drops below 9.5, or when the concrete's alkalinity diminishes, corrosion becomes inevitable.
In a real-world scenario, consider a methanol plant where reinforced concrete was exposed to chloride ions, resulting in substantial corrosion of the internal steel reinforcement. The plant's cooling tower, located in a marine environment, faced continuous exposure to marine air, moisture, and circulating saltwater, leading to severe corrosion over the years. A third-party engineering firm was enlisted to assess the extent of saltwater penetration into the concrete. Initial findings revealed a concrete pH of 10.8, signifying an undeniable susceptibility to corrosion. As steel reinforcement corroded, the concrete's structural integrity was compromised, resulting in cracks and endangering the entire structure's design capacity.
To restore the cooling tower to its design capacity and prevent further corrosion, HJ3's CarbonSeal carbon fiber repair system was recommended. The repair proceeded in two phases. Phase one focused on the highest-priority area, the exterior supporting wall on the west side of the structure. In phase two, concrete columns along the north and south walls were reinforced. The process entailed the removal of spalling concrete using a high-pressure water jet. All exposed steel rebar was cleaned to a near-white metal state and safeguarded with a zinc-rich primer coating. Concrete was patched to achieve a uniform surface, primed, and the CarbonSeal high modulus paste was applied, followed by saturated CarbonSeal fabric. A chemical-resistant top coat was then applied for added protection.
HJ3's CarbonSeal system successfully strengthened the reinforced concrete walls and columns of the methanol production plant in just two phases, synchronized with the plant's planned outages. Remarkably, these repairs were completed on schedule despite challenging rainy and wet conditions that necessitated dry concrete before installing HJ3's CarbonSeal system. Subsequently, an earthquake occurred, and the CarbonSeal system demonstrated exceptional resilience, maintaining the cooling tower's structural integrity. The HJ3 CarbonSeal repair solution offers long-term protection and substantial cost savings compared to alternatives. It ensures structural strength, rapid implementation, and long-term corrosion prevention without the need for future maintenance.
If your steel or concrete infrastructure grapples with chloride ion corrosion, and you're eager to explore HJ3's CarbonSeal industrial repair systems, our project managers are ready to assist. Please reach out to us at hj3pm@hj3.com to learn more.
