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How VpCIs WorkHow VpCIs Work
nnHitek Electronic Materials LimitedHitek Electronic Materials Limited
This is a brief introduction to the technology involved in Cortecs Corrosion
Inhibiting products for more information please contact Hitek.
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VaporVapor--Phase CorrosionPhase Corrosion
InhibitorsInhibitorsDefinitionDefinition
nnVaporVapor--phase corrosion inhibitorsphase corrosion inhibitors
condition an enclosed atmosphere withcondition an enclosed atmosphere with
a protective vapor that condenses on alla protective vapor that condenses on all
metal surfaces (recessed areas,metal surfaces (recessed areas,
cavities)cavities)
The delivery of the protective vapour/ or molecule is one of Cortec's
strengths. These delivery systems include films sprays, foams and coatings
to name but a few. The vapour needs to be in a enclosure to make sure thatthere is sufficient of it to be effective, more of this later.
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VaporVapor--Phase CorrosionPhase Corrosion
InhibitorsInhibitorsHistoryHistory
nn US Navy (boilers, piping systems)US Navy (boilers, piping systems)
Late 1940sLate 1940s
It may be a surprise to those of you who havent heard of this technology
but it isnt new. Its been around since just after WWII, However at that
time it had very specialised applications, mainly in the military and thechemicals used were generally very toxic. Thanks to time and Cortec this
has changed dramatically.
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FactorsFactors
nnVapor pressureVapor pressure
nn DiffusionDiffusion
nn TemperatureTemperature
nnAir changeAir change
These are the factors that affect the effectiveness of the Vapour Phase
Corrosion inhibitor.
The first is the partial Vapour pressure of the vapour in the atmosphere, amore complete definition of this will be given in the next slide. The second
is diffusion the rate at which molecules in a high concentration area move
to a lower concentration area until equilibrium is achieved (Ficks Law)
The next item is temperature the higher the temperature the more rapid the
movement of the molecules and finally the rate at which the air is changed.
If the air is always changing there can be no build up of molecules on the
surface of the metal so there is no protection. In these cased coatings or
covers need to be employed
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Vapor PressureVapor Pressure
nnVapor pressure:Vapor pressure:
The pressure exerted when a solid or liquidThe pressure exerted when a solid or liquid
is in equilibrium with its own vapor. Theis in equilibrium with its own vapor. The
vapor pressure is a function of thevapor pressure is a function of the
substance and of the temperaturesubstance and of the temperature
Here is the text book definition of vapour pressure note that vapour
pressure is a function of temperature. It should be noted that the vapour
pressure exerted from a solid at a given temperature tends to be extremelylow. Most of Cortec emitters are in solid form. It was one of the challenges
in the development of Cortec's patented technology that the required vapour
pressure be low so that the resulting life of the delivery system would be
long enough to make it economic.
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Vapor PressureVapor Pressure
VCI AVCI A VCI BVCI B
This is just a slide illustrating vapour pressure not that the pressure exerted
by VCI A is lower than that of VCI B
Under the same conditions.
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Vapor PressureVapor Pressure
nnAtmospheric pressure: 760 mm HgAtmospheric pressure: 760 mm Hg
nn Water: 18 mm Hg at 68F (20C)Water: 18 mm Hg at 68F (20C)
nn Typical VCI: 10Typical VCI: 10--44 mm Hg at 68F (20C)mm Hg at 68F (20C)
nn Sodium nitrite: ~ nilSodium nitrite: ~ nil
This is a table showing the various pressures exerted at atmospheric
pressure by various vapours at around room temperature. Note that the
Sodium nitrite does not exert a vapour pressure at this temperature. SodiumNitrite corrosion inhibitors for steel need to come into contact with the
surface at this temperature in order to be effective. They have been around
for about 30years and should really be classed as contact corrosion
inhibitors, unless being used at considerably higher temperatures. Sodium
nitrite is only good for ferrous metals, unlike the Cortec materials which are
multimetal compatible. There have been some serious issue with staining
and embrittlement of platings and metals when using sodium nitrite based
coatings and films.
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DiffusionDiffusion
nn Diffusion governed by Ficks LawDiffusion governed by Ficks Law
VCI molecules diffuse from a high VCIVCI molecules diffuse from a high VCI
concentration region to a low VCIconcentration region to a low VCI
concentration region until equilibrium isconcentration region until equilibrium is
reachedreached
Here's the text book definition of diffusion
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VCIVCI
SourceSource
DiffusionDiffusion
High Concentration
Low Concentration
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TemperatureTemperature
nn The higher the temperature, the higherThe higher the temperature, the higher
the vapor pressurethe vapor pressure
The higher the temperature the higher the rate of depletion of the delivery
system. For most Cortec products at around 20C the life is approx 2years.
If a higher ambient temperature is expected the souces need to bereinforced with additional foams and coatings to extend the life.
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Air ChangeAir Change
nnAccelerates the depletion of VCIsAccelerates the depletion of VCIs
nn Judicious placement of the VCI sourceJudicious placement of the VCI source
can reduce the effect of air changescan reduce the effect of air changes
As mentioned before if you change the air you reduce the effectiveness of
the solution
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So here is the graphic representing what we have discussed. The VCI
souce at the top, exerts a vapour pressure in the enclosure. The molecules
are drawn to the metal surface and protect it with a monomolecular layer ofthe vapour that are very fond of bonding to the metal. The bond however is
not strong and is always being replenished by the vapour in the enclosure.
It is a dynamic equilibrium.
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MetalMetal
How to Weather BadHow to Weather Bad
Conditions?Conditions?
Think of each molecule as a little umbrella that protects against the adverse
weather conditions
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MetalMetal
WaterOxygenContaminants
Lots of these line up to protect against the elements that attack the metal
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MetalMetal
And they continue to work whatever the weather, making you happy
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VaporVapor--Phase CorrosionPhase Corrosion
InhibitorsInhibitorsBenefitsBenefits
nn Cost effectiveness (VCI/barrierCost effectiveness (VCI/barrier
bags+dess.)bags+dess.)
nn Ease of use (recessed areas)Ease of use (recessed areas)
nn Cleanliness (thin layer)Cleanliness (thin layer)
nn
Safety/Environment (LD50)Safety/Environment (LD50)
The really good thing about Cortec Corrosion inhibitors is that they are cost
effective, they are easy to use and
Are very clean, the monomolecular layer is un-noticeable. The moleculeitself is derived from vegetable matter making it relatively safe when
compared with sodium nitrite
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Cortecs VCIsCortecs VCIs
nn MultiMulti--metal protection (VCImetal protection (VCI--126)126)
nn MultiMulti--functional (VCIfunctional (VCI--125, VCI125, VCI--377)377)
nnVery low toxicity (VCIVery low toxicity (VCI--309)309)
nn Environmental friendly (ISO 14001)Environmental friendly (ISO 14001)
nn Superior quality system (ISO 9001)Superior quality system (ISO 9001)
So here are some of the main features and benefits of using Cortec
Corrosion inhibitors
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Test MethodsTest Methods
nnVapor Inhibiting Ability (Fed. Std. 101C)Vapor Inhibiting Ability (Fed. Std. 101C)
These are the test methods used by Cortec to test their products
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Important ParametersImportant Parameters
nn Surface cleanlinessSurface cleanliness
nn Surface finishSurface finish
nn ConditioningConditioning
nn ContaminantsContaminants
nn Source exhaustionSource exhaustion
nn OthersOthers
Here are some of the factors you need to be aware of before you start, if you
do not address them then the VpCI will not work, for example if the surface
is encrusted with dirt the molecule will not be able to reach the surface.
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Defining PerformanceDefining Performance
nn ProtectionProtection
Long/short termLong/short term
Distance from sourceDistance from source
nn ConditionsConditions
HumidityHumidity
TemperatureTemperature Corrosive agents, contaminantsCorrosive agents, contaminants
You need to define what you want to do and what conditions it will be in
Cortec as different solutions based on the same technology depending on
your needs
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ConclusionsConclusions
nn CorrosionCorrosion
nn Corrosion preventionCorrosion prevention
nn Corrosion inhibitorsCorrosion inhibitors
nnVaporVapor--phase corrosion inhibitorsphase corrosion inhibitors
nn Cortecs VCIsCortecs VCIs
nn BenefitsBenefits
nnApplicationsApplications
If you want a cost effective solution to your corrosion problems consider
Cortec and Hitek
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