FAQs

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.

VCI stands for Volatile or Vapor Corrosion Inhibitors. ZERUST® applies VCI technology to inhibit corrosion on metal surfaces. VCI film is packaging that generally consists of polyethylene film that has been impregnated with chemical formulations that are unique to each manufacturer. While the underlying formulations can vary significantly, the finished products function similarly in that they release very low concentrations (typically in parts per ten-thousandth) of invisible corrosion inhibiting vapors into the surrounding air. The vapor molecules subsequently condense onto exposed metal surfaces and form a molecular corrosion shield that can protect against rust and other forms of corrosion for many years. Typical service life is up to three (3) years and even longer in some cases. When the VCI packaging is later removed, all vapor corrosion inhibiting molecules rapidly evaporate. This leaves the metal parts clean and ready for immediate use.

Corrosion is the chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. Usually, corrosion is the oxidation of metals in the presence of water or water vapor and is known as rust (iron, steel), white rust (galvanized steel), and other terms of corrosion failures such as tarnish, pitting, and flaking.

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.

Nitrates (NO₃ – one nitrogen and three oxygen molecules) are compounds that occur naturally in soil. Consequently, nitrates are also present naturally in root vegetables like carrots and potatoes, as well as leafy green vegetables. Nitrates are not generally harmful unless they are consumed in massive quantities. When we eat nitrates, they are converted into nitrites in our digestive system.

Nitrites are also compounds made up of nitrogen and oxygen, but instead of three oxygen molecules, they have only two (NO₂). Nitrite compounds combine with other elements like sodium and potassium to make sodium nitrite or potassium nitrite, which are used as preservatives and color fixatives in cured meats. Nitrites are particularly good at preventing botulism – an anaerobic form of bacteria that causes paralysis and death – which is why small amounts of sodium nitrite are required by law to be added to cured meats. Nitrites too, on their own and in moderation, are also generally not harmful.

Sodium nitrite, however, isn’t just a good food preservative, it’s also an excellent corrosion inhibitor. That’s why, when NTIC developed and commercialized the first-ever VCI rust preventative plastic packaging, the active chemical protection system was formulated using common food additives, including sodium nitrite. Conservative chemists generally do not recognize sodium nitrite itself as a vapor corrosion inhibitor because, on its own, it has a vapor pressure so low that it is almost immeasurable. When used in combination with other additives in proprietary ZERUST® formulations, sodium nitrite can be effective “VCI activated”. The ZERUST® VCI effectiveness has been proven in commercial and military applications worldwide, as well as scientifically by recognized standard test methods for vapor corrosion inhibitors used by U.S. and NATO military organizations.

Nitrites in VCI products are a commonly misunderstood safety concern because of the historic use of the specific compound, dicyclohexylamine nitrite (or dicyclohexylammonium nitrite). Sometimes referred to by the brand name “Dichan”, dicyclohexylamine nitrite is a vapor corrosion inhibitor that was first used in VCI paper production in the 1940’s. Later, in the 1970’s, toxicologists started to become aware that compounds using both amines and nitrites in combination could lead to the formation of “n-nitroso amines”, which are believed to be both carcinogenic and genotoxic. It is for this reason that VCI products produced in most advanced industrialized nations no longer use dicyclohexylamine nitrite. ZERUST® VCI packaging has never contained dicyclohexylamine nitrite and, furthermore, does not use amines of any kind because they are known to be skin and respiratory irritants.

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.

Tests performed with electron spectroscopy for chemical analysis (ESCA) show that 2-4 hours after a steel panel is removed from a ZERUST® VCI package, all traces of the corrosion inhibiting molecular layer are gone from the surface of the part.

The period of time before one can expect corrosion to occur on a part depends on the cleanliness of the part and the environment around the part (relative humidity, presence of pollutants or wood, temperature, etc.)

The time required for active corrosion inhibiting molecules from a VCI product to saturate a package is a function of the volume and temperature of the package. Therefore, protection begins as soon as corrosion inhibiting molecules reach the metal surface, and maximum protection is achieved when the entire environment of the package is saturated with the corrosion inhibiting molecules.

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®.

Yes. Our internationally recognized scientists and corrosion engineers work closely with customers to design and implement comprehensive corrosion management systems. As part of the validation process, customer parts along with proposed rust preventative solutions can be subjected to accelerated corrosion testing in the various climate stress simulation chambers available at our technical support laboratories that are strategically located in major industrialized regions around the world.

VCI Bags, or Vapor Corrosion Inhibitor bags, are made with poly packaging film converted to a bag manufactured with added VCI chemistry. VCI molecules protect metals from corrosion by forming a thin, invisible layer on the surface. This layer inhibits the corrosion process caused by oxygen, water, and contaminants. VCI bags are typically used when you want to protect metal parts from rust during storage or shipment but don’t want to paint or coat the parts in a rust preventative coating.

VCI Paper, or Vapor Corrosion Inhibitor, paper emits VCI molecules that settle on metal surfaces and form an invisible layer that protects from rust and corrosion. VCI Paper protects by interrupting the electrochemical corrosion process caused by moisture, oxygen, and contaminants in the atmosphere.

Most ZERUST®/EXCOR® VCI film products have a shelf life of up to three years when the product is stored in original airtight packaging, out of direct sunlight, and under shelter. Other products such as VCI Kraft paper, VCI emitters, liquids, and rust removers may have a shorter shelf life. Please refer to each product’s infosheet for the correct shelf life.

ZERUST®/EXCOR® VCI provides effective corrosion protection for clean metals for years^‡ when used correctly and utilized within three (3) years from receipt. ZERUST®/EXCOR® VCI products should be stored in original packaging away from direct sunlight in conditions below 85°F (30°C) and 50% RH until it is ready for use.

The component/part or volume needing protection must be completely enclosed by a ZERUST®/EXCOR® active material (VCI Poly/VCI Paper). If complete ZERUST®/EXCOR® packaging is being used, no additional VCI material is required. However, this also depends on the nature of the packed merchandise. If there are difficult-to-access areas, it is advisable to use additional ZERUST®/EXCOR® VCI Emitters and Diffusers to add additional protection.

ZERUST®/EXCOR® VCI film and bags can be reused if they are dry, clean, and undamaged. Small holes in the VCI film material can be sealed with adhesive tape. VCI bags that have large holes or tears or have begun to crack or lose strength due to excessive exposure to direct sunlight will not provide adequate corrosion protection and should not be reused.

The more tightly sealed the VCI packaging, the better the volatile corrosion protection. Seals may be closed with zip-ties, packaging tape, or staples. A good closure method is to fold over the film and either tape or staple the area shut. When stapling, seal over the holes made by the staples with tape. The best seal is always a heat seal, but it is not necessary. Also, it is unnecessary to extract air from the enclosure before sealing to prevent future airflow. Water must be prevented from penetrating the packaging. Be careful to fold over the film and close VCI gusset bags so water cannot easily pool and enter the enclosure.

Use a high-quality packaging tape that is designed to adhere to low-energy surfaces like polyethylene or, you can fold over and staple the area shut and then seal over the holes made by the staples with the recommended tape. If you have a large rip that you cannot close easily with tape or staples, you should replace the bag with a new one. The best seal is always a heat seal.

After removal of ZERUST®/EXCOR® packaging, the VCI substances present on the metal surface disperse within one to two hours.

Both VCI packaging products are useful, but one may be a better option depending on the application. VCI paper releases VCIs more rapidly than VCI film, but does not have as long of a service life. VCI film acts as a barrier to water vapor, whereas dry paper readily absorbs moisture. Other characteristics of the product needed could include formability, visibility of parts, and outer packaging used. The application should be oriented toward the goods to be protected and the details of the manufacturer’s packaging operations. A ZERUST®/EXCOR® representative can advise you on this.

A light oil coating on the metal part is fine to use with ZERUST®/EXCOR® VCI bags and film. A heavy oil coating may affect the performance of the VCI bag by keeping the vapor corrosion inhibiting molecules from reaching the metal surface. Please contact ZERUST®/EXCOR® to determine the suitability of the oil and application.

Ferrous: Iron, steel, and cast iron metals are protected using ZERUST®/EXCOR® Ferrous Packaging.
Non-Ferrous: Aluminum (and aluminum alloys containing copper and/or manganese), copper, brass, bronze, and fully galvanized steel are protected using ZERUST®/EXCOR® Non-Ferrous Packaging.
Multimetal: Products that contain combinations of the Ferrous and Non-Ferrous metals listed above can be protected by ZERUST®/EXCOR® Multimetal Packaging.
Silver: Is protected from tarnishing with ZERUST®/EXCOR® anti-tarnish packaging or film with acid-gas scavenger additives.

ZERUST®/EXCOR® trademark color is yellow for VCI film. We also offer stock items in blue, green, clear, and gray. We can custom produce most products in any color of your choice.

If you have any questions regarding the best VCI protection for your needs, we advise consulting a ZERUST®/EXCOR® representative. ZERUST®/EXCOR® possesses wide-ranging testing capabilities, which quickly enable us to determine the optimum method of protecting a given metal item. We also can send samples for customers to conduct their own tests. First, try packing identical parts simultaneously and under identical conditions, one part in a normal film or your current packaging and one in ZERUST®/EXCOR® film. Next, store these parts for several days in the most challenging conditions they will be in, such as high humidity, or move them from warm to cool places in your warehouse, similar to shipping conditions. If the part packed in normal packaging shows signs of corrosion, while the one packed in ZERUST®/EXCOR® VCI film shows none, it can be assumed that the part requires VCI protection.

Each order is tested by ZERUST’s Quality Control Department to ensure that it meets our quality standards for corrosion protection and material performance. Part of the quoted lead time is used for this quality testing. If you’d like to waive this quality testing on your product, you must sign a Quality Testing Waiver Request form. Please contact your service representative for more information.

Yes, Northern Technologies International Corporation, the maker of ZERUST®/EXCOR® products, operates a quality management system for the design and manufacture of corrosion inhibiting and protective packaging systems that are certified to conform to the ISO 9001:2015 Quality Management Standard.

Yes. ZERUST®/EXCOR® VCI films made of polyethylene and polypropylene can be recycled at facilities for PE/PP processing or incinerated.

ZERUST®/EXCOR® VCI packaging products are produced using only virgin materials to ensure high quality and consistency for our customers. However, environmental consciousness is on the rise. As a result, companies are increasingly seeking innovative ways to reduce their carbon footprint and promote sustainability. Consequently, one such approach that’s gaining traction is post-consumer recycling. Here at ZERUST®, we’re at the forefront of implementing this technology across our VCI polymer film solutions. Furthermore, by incorporating post-consumer recycled materials into our VCI polymer packaging products, ZERUST® is reducing the demand for virgin plastics and promoting the circular economy. Moreover, by choosing ZERUST® products, businesses can protect their metal assets, reduce their environmental footprint, and join the global effort to build a more sustainable and responsible future!

To purchase ZERUST® VCI products, you can either call 1-800-328-2433 or 1-763-225-6600 to speak with a customer service representative or send an email to sales@ntic.com.

For flat bag, sheet, sleeve, and round bottom bags.

You may also try our bag calculator to help find the right sized back for you.

NTIC’s stock products ship from centrally located warehouses in the United States. In stock products ship within 1-2 days. Some stock liquid and powders require 5-7 days for repacking certain sizes. Your customer service representative can advise you of your products handling time and estimated shipping time.

NTIC’s custom product lead times vary depending on the product and quantity. Typical lead times for custom products are 3-4 weeks. Some specialty product features or additives can take 8-10 weeks. For specific product inquiries, please contact our customer service team.