ZERUST® Cor Tab® VCI Tablets

VCI Emitters (also known as VCI diffusers) emit powerful ZERUST® corrosion inhibiting molecules into an enclosure that settles on metal surfaces and protect them from rust and corrosion. VCI Emitters provide targeted corrosion protection in hard-to-reach enclosed spaces for electronics or can be used as added protection to ZERUST® VCI packaging products.

Vapor corrosion inhibitors (VCI) are substances that slowly release a corrosion preventative compound into a sealed air space, effectively protecting exposed metal surfaces. VCIs are often used in situations where it is impractical or undesired to use rust preventative liquids or other surface treatments.

ZERUST® VCI products prevent corrosion in several ways:

1. By acting as a protective barrier from external corrosive atmospheric elements such as abrasion, water, dirt, and acid gas pollutants.
2. By emitting Volatile Corrosion Inhibitors that passivate the electron flow between the anodic and cathodic areas on metal surfaces and interrupt the electrochemical corrosion process.
3. By adding water repulsion properties to the metal surface, which inhibit water from permeating the metal surface and providing the electrolyte for corrosion reactions.

The vapor corrosion inhibitor portion of ZERUST® VCI products is made of proprietary chemical formulations that are invisible, odorless, non-toxic, non-reactive, non-flammable, and non-allergenic. These chemical formulations release a corrosion inhibiting vapor that diffuses throughout an enclosure that either contains VCI formulations or is made from VCI materials and settles on exposed metal surfaces to form a microscopic corrosion inhibiting layer.

This protective layer will remain on the surface of the metal if there is no significant, continuous exchange of air within the enclosure. Ideally, there should be less than one air exchange per day (for example, when an electrical cabinet or package is opened briefly and occasionally). Once the metal part is removed from the enclosure, the corrosion inhibiting layer is no longer kept in place by equilibrium with the VCI source, and it dissipates from metal surfaces (typically within about an hour), leaving the metal part clean, dry, and corrosion-free.

The vapor diffusing properties of our corrosion inhibiting formulations offer an important advantage over conventional inhibitor coatings since the traces of these gas molecules penetrate hard-to-access crevices, gaps, and slots. They also cover the surfaces of complex-shaped articles that are difficult to coat. They are adsorbed onto the surface of the metal to form a corrosion inhibiting protective layer that is just a few molecules thick. ZERUST® VCI products may also include acid gas absorbing chemicals in the packaging material to act as a barrier and add another dimension to the protection of the metal content. These “scavenging” chemicals react and neutralize the polluted air that may diffuse through the ZERUST® VCI material. Also used are various combinations of physical barrier properties that optimize the corrosion prevention and physical protection needs of our customers. These may range from plain low-density polyethylene (LDPE) material to combinations of higher strength, higher tear resistance, higher resistance to sunlight or UV, static charge dissipation, and lower diffusion for moisture or acid gas molecules.

ZERUST® VCI products offer corrosion protection without having to be in direct contact with or coated onto the parts that are being protected. Metal parts merely need to be enclosed in or with a ZERUST® VCI product (where airflow is minimized) for protection to occur. With ZERUST® VCI packaging, it is no longer necessary to apply messy oils, greases, and other corrosion protection compounds and incur the cost of their removal.

Depending on the design of the corrosion prevention solution, some ZERUST® VCI packaging products may be produced from low and high-density polyethylene resins that are resistant to vapor penetration. Some atmospheric moisture will eventually find its way into a closed package. The presence of moisture in a package can be expected during shipments across areas of high humidity.

When moisture permeates through the ZERUST® VCI plastic packaging products (flexible and rigid), the moisture is affected by the vapor corrosion inhibitors that are present in the VCI product. As a result, the ZERUST® VCI products inhibit corrosion despite a low level of moisture passing through the plastic. Corrosion problems arise when moisture can enter a package unimpeded by the packaging products, such as through an incorrect closure or a significant hole in the package. For example, when there is a significant breach in the package, the corrosion inhibiting molecules can escape, breaking up the protective corrosion inhibiting molecular layer that had formed on the surface of the metal. Therefore, an unimpeded airflow into the package must be avoided.

ZERUST® VCI technology provides active corrosion protection. ZERUST® products release invisible, odorless, non-toxic vapor corrosion inhibitor (“VCI”) molecules. A ZERUST® bag, for example, will actively continue to release VCI molecules until the air inside the bag is completely saturated. The protective ZERUST® VCI molecules will then adsorb themselves to all the surfaces on any metal product(s) inside this bag, forming a transparent, self-repairing, rust-protective layer. This nano-layer of corrosion preventative molecules, in turn, actively passivates the metal surfaces, thereby preventing electrochemical reactions that might otherwise cause rust or corrosion.

Desiccants provide passive corrosion protection. Just like a sponge, desiccants absorb moisture from the surrounding atmosphere. The reduction in ambient humidity can prevent the formation of electrolytes on metal surfaces that might otherwise activate electrochemical corrosion reactions. However, desiccants have a very finite limit to the maximum amount of water they can absorb. Once this is exceeded, desiccants cease to provide any further protection. Worse, they may even leak moisture back into their surroundings.

ZERUST® VCI paper/plastic packaging does not affect the functionality of electronic circuitry, nor negatively react with non-metallic surfaces such as plastics, rubbers, or wood. However, since there are so many possible combinations of chemistries, materials, processes, and substrates, we always recommend contacting a ZERUST® account manager to validate the application. Other rust prevention methods such as oils, greases, and other liquid RPs (rust preventatives) pose a much higher likelihood of reacting with plastics, rubbers, and wood.

When a corroded item is packaged in ZERUST® VCI products, the corrosion process is slowed. However, our packaging products cannot remove corrosion that has already formed.

When wet parts are packaged in ZERUST® VCI products, a certain amount of corrosion can be anticipated to take place. The amount of corrosion will be a function of the time it takes for the active corrosion inhibiting molecules to saturate the package enclosure, the corrosion inhibiting effectiveness of the designed VCI system, the amount of moisture on the part, and the pH and contamination of the water itself.

Test data show that ZERUST® VCI products do not adversely affect electrical and electronic components. In fact, the corrosion inhibiting molecules help improve the reliability of electrical and electronic components by preventing corrosion that is too small to be seen by the naked eye. Therefore, it is safe to use ZERUST® VCI packaging products to prevent corrosion of any instruments, devices, and equipment that contain electric and electronic components.

Test data and review of corresponding scientific literature show that there are no inhalation or contact risks with ZERUST® VCI products. ZERUST® VCI products have been reviewed and cleared for use by factory, government, and military personnel by the appropriate occupational health departments, including those of most major automotive manufacturers worldwide.

ZERUST® has extensive experience in corrosion prevention and remediation for the military. Many ZERUST® products have Mil Specs, NSN numbers and are listed on the GSA schedule. We are dedicated to serving all branches of the military and their unique needs. Contact customer service for military applications and sales inquiries.

Keep VCI products in original packaging until use. Store in a dry, covered warehouse between 0°F to 85°F (-18°C to 29°C) with a relative humidity of less than 60%. When not using ZERUST® VCI material for an extended period, enclose it in airtight plastic packaging to prevent atmospheric contamination and preserve the VCI. Reclose packaging at the end of shifts or during downtime.

There are many ways to prevent corrosion, including modifying the atmosphere by dehumidification, nitrogen purge, evacuation, etc., and creating a barrier on the metal surface to prevent the permeation of moisture. This barrier can be formed by liquid coatings, such as oil, or via packaging products that contain VCI or Vapor Corrosion Inhibitors. Vapor Corrosion Inhibitors work by diffusing corrosion inhibiting molecules from a source (packaging film or paper, for example) to metal surfaces. These molecules settle on metal surfaces and form a protective corrosion inhibiting layer that inhibits the electrochemical reactions that cause corrosion to form.

ZERUST® combines the use of vapor corrosion inhibitors with material sciences and process management expertise to implement custom corrosion solutions for a customer or throughout an entire supply chain. We call this our ZERUST®/EXCOR® Integrated Corrosion Technologies or ICT®.

The compounds that VCIs release into an airspace actively prevent corrosion by forming strong bonds with a metal surface, promoting and maintaining the natural and healthy passive oxide layer on the metal. The VCI layer that forms is invisible, dry, and does not affect the physical properties or functionality of the metal in any way. Therefore, the protected metal can be painted, treated, and/or used straight out of the ZERUST® packaging without further cleaning.

“VCI” stands for Vapor corrosion inhibitors. These corrosion inhibitor compounds emit from the VCI paper, film, or emitter and settles on the metal surface to form an invisible layer that prevents oxidation by interrupting the electrochemical corrosion process caused by moisture, oxygen, and contaminants in the atmosphere.