As seen in the August/September 2017 Issue of Pollution Equipment News
Facility upkeep is an important long-term strategy for increasing the service life of plant structures and equipment. Deterioration of structures through corrosion and lost efficiency through scale buildup are normal processes that happen over time. These natural mechanisms accelerate in certain conditions such as high humidity, high temperatures, or the presence of corrosive gases. If left untreated, corrosion and scale can impact the performance of critical equipment and shorten the service life of facility assets. To avoid these problems, minimize downtime, and maximize facility lifetime, it is helpful to take simple preventive steps that are sometimes overlooked.
Minimizing Replacement and Downtime of Electricals
Facilities rely on hundreds to thousands of electrical control panels, control boxes, and wire-ways to keep operations running smoothly. Corroded electrical contacts could result in failure and downtime and require extra labor to repair or replace. Corrosion protection minimizes these interruptions and costs and is easy to achieve with the use of vapor phase corrosion inhibitor technology.
This technology comes in many forms, including VpCI emitters. These are small self-stick cups that emit corrosion inhibiting vapors through a breathable lid. When placed inside an enclosure such as an electrical cabinet, the inhibitor vapors diffuse to fill the enclosed space, then condense and form a protective molecular layer on all metal surfaces inside the area. The layer protects multiple metals from corrosion and does not interfere with electrical performance.
To maximize protection of electricals, a Corrosorber cup, similar in appearance to a VpCI emitter, can also be placed in electrical equipment. The Corrosorber contains a material that absorbs corrosive gases such as hydrogen sulfide and volatile mercaptans, so that they are not free to damage metals. As the corrosive gases are absorbed and trapped, the material inside the Corrosorber changes color from off-white to black to indicate that it is spent.
Another helpful strategy for minimizing corrosion on electronics and electricals is to spray a thin film coating on circuit boards, electrical contacts, motors, generators, and junction boxes using a VpCI electronics cleaner such as ElectriCorr VpCI-238 or VpCI-239. This creates an extremely thin film that protects metal surfaces directly in contact with it. It also adds a degree of vapor protection to protect surfaces that may have been missed by the spray.
Maximizing Protection and Efficiency of Process Water Equipment
Industrial plants often include boilers and other closed loop heating and cooling systems that can benefit from corrosion inhibitor/scale removal maintenance. Scale and oxide build-up inside water systems, heat-exchangers, cooling towers, and pipes reduce system efficiency and obstruct water flow. This can be addressed with an eco-friendly treatment such as EcoClean Biodegradable Scale and Rust Remover, a USDA Certified Biobased Product that can be thrown in water-soluble pouch form into portions of the system affected with scale buildup. As the product circulates, it works to remove scale and rust even from hard-to-reach areas, while protecting the freshly exposed metal against flash rust. The overall benefits are improved process water flow and enhanced system efficiency.
For long-term protection of process water systems during facility operation, vapor phase corrosion inhibitor additives can be added to the systems in low doses at very low or no toxicity. In addition to protecting surfaces in contact with the treated process water, the vapor phase action of the inhibitors provides protection to metal surfaces above the water level where traditional contact inhibitors cannot reach. If for some reason the system needs to be drained for temporary layup (e.g., seasonal changes), an additive such as VpCI-649 can be circulated through the system and drained, leaving residual protection and allowing easy disposal because of the absence of nitrites, phosphates, chromates, and heavy metals. Heat system boilers laid up for the summer can be more easily and effectively treated with vapor phase corrosion inhibitors because the inhibitors do not need to be directly applied to all surfaces, and because they can be left inside and circulated when the system is restarted.
Minimizing Labor on Coatings Application
Coatings application is a must for the many metal surfaces inside an industry facility. Metal stairways, tanks, and miles of piping all need protection and stand to benefit from coatings enhanced with organic corrosion inhibitors. VpCI coatings protect with a thin molecular layer that lines micro-cavities in the metal surface, unlike traditional sacrificial metal corrosion inhibitor coatings that rely on zincs or chromates. Due to their large particle size, these heavy metals leave gaps that can allow the start of micro-corrosion, eventually leading to coating failure. VpCI coatings discourage the spread of corrosion and achieve protection at a lower dry film thickness, requiring the purchase of fewer materials and reducing labor.
Good surface preparation and use of a two-coat system are still important keys to ensuring the best performance of a coating. This is often a challenge on rusty surfaces. A common solution is sand-blasting, which is time-consuming, labor-intensive, and not always feasible. An excellent alternative is to remove loose rust from the metal surface, and then to apply CorrVerter, an environmentally-friendly water-based primer that converts rust into a hydrophobic passive layer. A VpCI topcoat can be subsequently applied at a low dry film thickness, making the whole process easier and less labor-intensive.
Maximizing the Service Life of Concrete Structures
Reinforced concrete is a common material found in industrial plant foundations, floors, walls, tanks, and tunnels. Initially, the embedded reinforcement is protected from corrosion because the pH of new concrete forms a passive layer on the rebar. However, as time passes, carbonation lowers the pH of the concrete and the passive layer disappears. The metal reinforcement is then vulnerable to the ingress of corrosive contaminants—oxygen, moisture, chlorides, and industrial pollutants—that initiate corrosion. As the corrosion products build on the surface of the rebar, the resulting pressure creates cracking and spalling of the concrete. This increases exposure to corrosive elements, and the cycle continues to accelerate structural deterioration.
Migrating corrosion inhibitors applied as an admixture to new construction or as a topical treatment to existing structures slow this process down. The migrating inhibitors work their way through the concrete pores by capillary action (when applied as a liquid) and vapor diffusion, forming a protective molecular layer on the surface of the rebar. This layer protects at both the anode and cathode of a corrosion cell, significantly reducing corrosion even in the presence of cracking. Migrating corrosion inhibitors can slow the time to corrosion initiation, dramatically reduce corrosion rates once started, and extend the projected service life of a concrete structure.
Figure 3: Migrating corrosion inhibitors travel through concrete to protect the surface of embedded steel reinforcement. Image Credit: Cortec Middle East.
By taking basic steps like these to protect against corrosion and scale, facilities can help minimize corrosion downtime, increase efficiency, and extend the lifetime of plant equipment. Vapor phase corrosion inhibitors and migrating corrosion inhibitors are important parts of making that happen simply and effectively.
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