Rustproofing Limitations
Undercoating and spray-on type rust proofing (rustproofing) insulates the
metal from moisture and oxygen by covering it with a protective coating.
There
are two main disadvantages of this method.
-
It's
impossible to cover every area on the vehicle with this method and hard to
reach places are left unprotected, often these are the areas that are most
prone to corrosion.
-
It's
effective as long as the protective surface is not damaged. In real terms
this is not possible and where damage occurs, no matter how small, rust
will occur. Cracking at the body
joints, stone chips, scratches, peeling and brittleness of the
undercoating can result in water getting trapped between the metal and the
undercoating allowing rust to form where you can't see it until it's too
late. This is why many rust proofing and undercoating companies recommend
that you get your car or truck inspected and re-sprayed every year. This,
of course, costs you more money.
Even if your vehicle already has some type
of undercoating it will probably still rust.
RustStop® RS-5 electronic rust protection compliments any
undercoating or spray-on type rustproofing
(rust proofing) application giving maximum effectiveness.
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Capacitive Coupling, used by some products, relies on the
paint as a dielectric or barrier to the free electrons, causing the metal to
be at a lower potential difference, theoretically slowing rust formation.
Contrary to the false claims you may have seen, the facts
are, there are two main problems with Capacitive Coupling for vehicles.
Firstly, if there are stone chips or cracks in the paint,
the dielectric (barrier) is broken and hence the charge is lost. So you need
to make sure that there is no bare metal, chips or cracks on the vehicle,
which is impractical.
Another problem is that it is almost impossible to hold a
charge (potential difference) on a sharp thin edge of metal, and so this
technology is not really suited for vehicles, which are made up of many
irregular shapes. Because of this, it is also ineffective on existing rust
and the areas surrounding it, as rust always causes sharp edges and damaged
paint work.
One ridiculous claim out there about Capacitive Coupling says that the
problem areas (mentioned above) get even greater protection. If that is
truly the case, why is the paint needed as a dielectric or barrier in the
first place?
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According to the U.S. Navy, Cathodic Protection is the
best form of electronic corrosion control. It is widely used at Naval Shore
Activities for protecting buried and waterfront structures and for
protecting the interiors of water storage tanks. In some cases, such as
underground pipelines, their field experience has shown that cathodic
protection is such an effective means of providing the required levels of
safety in the operation of the systems that they require Cathodic Protection
by regulation.
Cathodic protection is one of the few
methods of corrosion control that can be effectively used to control
corrosion of existing metal surfaces. Thus, if corrosion is occurring,
cathodic protection can be applied to stop the corrosion damage from
increasing. Cathodic protection can, however, only stop further corrosion
from occurring and cannot restore the material already lost due to
corrosion.
Corrosion is basically an electrochemical
process. That is, it is a process where chemical reactions take place
through the exchange of electrons. Cathodic Protection systems prevent the
corrosion reactions that would otherwise naturally occur by preventing the
exchange of electrons.
As in any electronic process, the positive side, the
anode (we'll call it "natural anode"), gets eaten away while the negative
side, the cathode, is protected.
Metal
ordinarily behaves like a natural anode and corrodes. Cathodic protection
prevents corrosion by making a metal behave like a cathode and be free from
corrosive attack. This is achieved by providing electrons of a higher energy
level (electric potential) than those
which would be produced in
the corrosion reaction at the natural anode.
Cathodic protection requires
a source of electrical current (high energy electrons) to prevent the
corrosive attack on metal. These sources of current are also called
“anodes” (we'll call them "protective anodes").
The method that is used to supply the
required current to the metal being protected depends on the type of
cathodic protection system being used, either Sacrificial Anode or Impressed
Current.
In Sacrificial Anode systems,
the current required for cathodic protection is supplied by the corrosion of
a protective anode made of an active metal such as
zinc or specifically developed aluminum, which has a higher positive charge
than the metal being protected (metal). This electric potential (Voltage)
difference causes a greater attraction of negative free electrons than the
ions in the metal. The result is that the protective anode now gets
sacrificed (corroded) and the corrosion process in the metal is interrupted
and hence protected.
In an
Impressed Current system, the current required is supplied by an external
power source. The effect of these electrons at the structure being protected
is the same as that derived from the sacrificial anode type of cathodic
protection system. However, the protective anode material, made from an
inert material such as high silicon cast iron, serves only as a source of
electrons and need not be consumed in providing protective current.
These two methods in their classical form rely on
water or the water contained in moist earth as an electrolyte (current path)
to complete the electrical process.
Obviously, vehicles are not covered with water or any
other electrolyte 100% of the time, so neither of these technologies in
their classical form are suited for vehicle rust protection.
RustStop® RS-5 uses both Sacrificial Anode and
Impressed Current Cathodic Protection.
To find out how we overcame the limitations of using
cathodic protection on vehicles,
click on:
What is RustStop® RS-5 electronic rust protection?
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Click
here to see: Why
RustStop®
is the right choice?
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