How Vci Work

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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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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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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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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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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

How Vci Work

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