Corrosion is a natural process where metals return back to its original state. Corrosion takes place in an electrochemical process where the electrolytes often found in the form of humidity causes the electrons to flow from anode to cathode on the unprotected metal surfaces.
Identification of Corrosion Case
- Identify metal types
- Identify metal grade
- Identify position and severity of corrosion
- Identify use or method of corrosion inhibitors
- Identify atmospheric conditions
According to NACE International (National Association of Corrosion Engineers), there are 17 different types of corrosion such as the uniform corrosion, pitting crevice corrosion, filiform corrosion, pack rust, galvanic corrosion, lamellar corrosion, erosion corrosion, cavitation, fretting corrosion, intergranular corrosion, exfoliation, dealloying, environmental cracking, stress corrosion cracking (SCC), corrosion fatigue, hydrogen embrittlement, and etc.
What Causes Corrosion? - Volatility and Conditions for Corrosion
- Relative Humidity - in general, corrosion begins in RH levels of 70% with presence of agents
- Exposure to corrosion agents – NO2, chloride, fluoride, sulfides (electrolytes in general)
- Volatility of aforementioned conditions
What Are the Most Common Cases of Corrosion?
- Common Industries: Oil & Gas, Packaging, Equipment/Machinery, Circuit Boards
- With the presence of corrosion agents (i.e. within open loop or closed loop systems)
- With the presence of microbiological organisms
- When there's human error in handling process
How Much Would Corrosion Cost?
According to WCO (World Corrosion Organization), NACE Interntational (National Association of Corrosion Engineers), CSSK (The Corrosion Science Society of Korea), (NDRC) National Development and Reform Commission, and CSCP (Chinese Society for Corrosion and Protection) the annual cost of corrosion worldwide is over 3% of the world’s GDP.
Corrosion Cost in USA: USD 276 billion
Corrosion Cost in China: USD 250 to 400 billion
Causes of Corrosion - Humidity inside Container
Changes in temperature during shipment leads to sudden evaporation and condensation inside the container, increasing humidity levels of up to 200%. High temperatures and ocean humidity causes the build-up of acid levels increasing the rate of metal corrosion at an exponential rate.
Causes of Corrosion - Moisture Absorbent Boxes
Starch in boxes absorbs moisture present in the atmosphere to a tune of 15-60% of the weight of corrugation. At room temperature the moisture levels absorbed in corrugation always exceed 15% threatening the packaged goods.
Causes of Corrosion - Plastics are Water Permeable
LDPE, HDPE have porosity of water also termed as Moisture Vapor Transmission Rate (MVTR) to the extent of 4 gms/sqm/24hrs. In order to make packaging full proof, chemicals need to be present inside the packaging to continuously neutralize moisture and inhibit the breathing of the plastic.
Volatile Corrosion Inhibitors (VCI)
VCI is a sophisticated yet economical way of protecting metals from corrosion. The atomic layer of VCI within the surface of the metal inhibits the electrochemical process. Our specialized eco-friendly VCI chemicals release corrosion inhibiting particles within the vapor area of the packaged metal. These VCI particles foam a thin protective layer about one molecule in thickness on the surface of the metal.
Effects of VCI
Chemical Coating of Metal Surface
A coated layer such as painting or greasing prevents oxygen in the air and water vapor from oxidizing with ions on the metal surface. However, painting and greasing when poorly maintained catalyzes rusting, not to mention added overhead costs to wash-off. VCI releases a chemical vapor which forms a chemical layer on the metal surface. This invisible layer of chemicals prevents oxidization, and naturally dissipates when air-flow is reintroduced.
The surface of metals isn’t in a stable state. The electrons of the metal ions are traveling freely and looking to bond and return to a stable state. When ions bond with O, OH ions suspended in the air, this leads to oxidization. VCI chemicals artificially create covalent bonds (stable) with the metal surface to stop anode-cathode electron transmission.
Vapor Pressure and Equilibrium
VCI creates an artificial atmosphere which prevents O, OH ions from freely moving in the close space. VCI chemicals have a much lower vapor pressure than water (20 mmHg) at 0.01-0.4 mmHg; therefore VCI doesn’t evaporate. VCI chemicals suspended in the air traps O, OH ions and create an artificial atmosphere which is rust-free.
- Safe to human
- Eco-friendly to the environment
- Does not contain nitrites, phosphates, chromes, or heavy metals
- Vapor-phase inhibiting action protects recessed and inaccessible surfaces
- Protected products can be shipped to customers without removal depending on types of VCI products
- Standard anti-corrosion protection for 2 years
- Little or no surface preparation is required after VCI packaging
- Reduces overhead cost as it is easy to apply and improves the handling productivity and safety
- The VCI layer does not need to be removed prior to processing or during the use of operation
- If required, the VCI may be easily removed by an air gun or water flush
- The application provides economical protection for various applications
Oil and grease are often used to provide corrosion protection other than VCI.
Oil and grease will provide short-term corrosion protection if they are fully coated onto protected parts, however, we do not recommend because of below reasons:
- Unsafe to human
- Hazardous to the environment
- Creates residue
- Requires removal
- Additional overhead costs
- Additional equipment required
- Does not provide long-term corrosion protection
VCI Application Fields are vast, including:
Extrusion machines, aircraft, machinery, aluminum, pipes, ship parts, auto parts, military, tanks, valves, boilers, marine, export packaging, metallic building materials, closed water cycle cooling system, liquid handling machine facilities, (KD) knock down export packaging, pipes, turbines, construction building materials, etc.