Volatile corrosion inhibitor

Volatile corrosion inhibitors (VCI) are a type of corrosion inhibitor that are used to protect ferrous materials and non ferrous metals against corrosion or oxidation where it is impractical to apply surface treatments.^[1] They slowly release chemical compounds within a sealed airspace that actively prevents surface corrosion. A typical application is to protect stored tools or parts inside bags, boxes or cupboards, one advantage of VCIs being that if the container is opened and reclosed, levels of inhibitor will recover.

History

The history of VCIs also known as Vapor Phase Corrosion Inhibitors (VpCIs), metal air inhibitors, vapor phase inhibitors (VPI) began in the 1940s when Shell Petroleum developed the very first of the traditional VCI's using a chemical compound called DICHAN or Dicyclohexylammonium Nitrite. This was used by the US military to prevent various metal components from corrosion and used it in multiple formats such as VCI paper, VCI powder, VCI solutions etc. Due to the dangerous nature of the chemistry DICHAN is now a mostly banned substance and there was a distinct break in the development of VCI's into two major groups of nitrite based VCI's and Amine based VCI's. The inclusion of either nitrite, secondary and tertiary amines is now frowned upon in the packaging world as combinations of these types of chemicals can cause Nitrosamines which are cancer forming agents.

The report Nitrosation of Volatile Amines at the Workplace [MAK Value Documentation, 1990]. The MAK Collection for Occupational Health and Safety. 24–37. shows nitrosation also can occur to primary amines: "N-Nitrosamines are formed in the nitrosation reaction from primary, secondary, and tertiary amines. The end product of the nitrosation of aromatic primary amines is a diazonium salt; with primary alkyl amines a mixture of products [4] is obtained which can also contain small amounts of dialkyl nitrosamines. In all these cases the first and rate-limiting step is an electrophilic attack by the nitrosating agent (NO · Y) on the free electron pair of the amine nitrogen. The amine is preferentially attacked in its unprotonated, basic form....

Amines can be converted to nitrosamines by reaction with nitrosation agents. Such nitrosation reactions can take place even under conditions which are far from optimal and, with few exceptions, the nitrosamines produced have proved in animal studies to be very potent carcinogens. Of the about 300 different N-nitroso compounds which have been tested to date, 90 % have been shown to have carcinogenic activity in about 40 species of animals; no animal species is resistant. The doses required for tumour induction are extremely small."

In July 29, 2004, Lynn Kenison, Senior Chemist for the USDOL OSHA Salt Lake Technical Center, wrote a report on his findings about VCIs and the need to include Material Safety Data Sheets (MSDSs). His finding included the following:

"1. VCIs are Hazardous Chemicals and do fall under the OSHA Hazard Communication Standard – 29 CFR 1910.1200. This means manufacturers must comply with the comprehensive hazard communication program explained above.

2. VCIs may present a Physical Hazard, a Health Hazard or both a Physical and Health Hazard. (a) PHYSICAL HAZARD – means a chemical for which there is scientifically valid evidence that it is a combustible liquid, a compressed gas, explosive, flammable, an organic peroxide, an oxidizer, pyrophoric, unstable (reactive) or water-reactive. (b) HEALTH HAZARD – means a chemical for which there is statistically significant evidence based on at least one study conducted in accordance with established scientific principles that acute or chronic health effects may occur in exposed employees. The term “health hazard” includes chemicals which are carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents which act on the hematopoietic system and agents which damage the lungs, skin, eyes, or mucous membranes.Appendix A of this standard provides further definitions and explanations of the scope of health hazards covered by this section. Appendix B describes the criteria to be used to determine whether or not a chemical is to be considered hazardous for purposes of this standard.

3. VCIs do not meet the definition of “articles,” but they do meet the definition of “Hazardous Chemicals”.

4. TRADE SECRETS – [29 CFR 1910.1200(i) thru (i)(1)(iv)] – The chemical manufacturer, importer, or employer may withhold the specific chemical identity, including the chemical name and other specific identification of a hazardous chemical, from the material safety data sheet, provided that: (a) The claim that the information withheld is a trade secret can be supported. (b) Information contained in the material data sheet concerning the properties and effects of the hazardous chemical is disclosed. (c) The material safety data sheet indicates that the specific chemical identity is being withheld as a trade secret. (d) The specific chemical identity is made available to health professionals, employees, and designated representatives in accordance with the applicable provisions of this paragraph – [29 CFR 1910.1200(i)(2) & (i)(3)]. (e) The name(s) of all other chemical(s) in the product is/are revealed along with their hazards.

5. Claiming ignorance (“I don’t know what is in this material and I don’t want to know!”) to avoid accountability, does not eliminate responsibility. Manufacturers are still responsible for the correct identification and warnings listed for each VCI.

6. ISO 9001 and ISO 14001 - apply to the processes that an organization employs to realize its products or services. In other words, the way it accomplishes its work and meets the customers’ requirements. ISO 9001 applies to the processes that influence product or service quality, and ISO 14001 applies to the processes that influence the organization’s environmental performance. ISO 9001 and ISO 14001 have nothing to do with “Product Quality” or “Product Guarantee”."

Product uses

VCI chemicals are often added to paper and plastic substrates as a medium to deliver the protective chemical compounds for use in automotive packaging, steel packaging, metal packaging, military and hobby markets.

Product Limitations

According to the US Military Packaging Manual (DLAM 4145.2, Vol. 1/TM 38-230-1/ AFP 71-15, Vol. 1/NAVSUP PUB 502, Rev. Vol.1/MCO P4030.31C):

(2) Restrictions and limitations in the use of VCI. VCI materials will not protect all metals from corrosion; in fact, they appear to increase the rate of corrosion in certain metals. VCI materials must not be used to protect any assemblies containing optical systems or precision moving parts which have been coated with a preservative or lubricant, unless otherwise specified. Items protected with bonded films, such as molybdenum (a dry lubricant), are not included in this category . VCI materials are affected by heat and light. They lose their effectiveness as the temperature increases and they decompose if exposed to direct sunlight for extended periods. They also decompose in the presence of acids or strong alkalies. Precautions must be taken when VCI is used with items, assemblies, and subassemblies containing zinc plate, cadmium, zinc. base alloys, magnesium base alloys, lead base alloys, and alloys of other metals including solders and brazing alloys. If such items contain more than 30 percent of zinc or 9 percent of lead, they must not be preserved with VCI. In all cases direct contact of VCI with non ferrous metals except aluminum and aluminum-base alloys should be avoided unless specific permission has been granted. Care should also be taken with assemblies containing plastics, painted parts, or components of natural or synthetic rubber. Assemblies containing parts made of these materials should not be packed with VCI until proof is established that they have passed the compatibility test required by Specification Mn..-I-8574.

See also

• Desiccant

References