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Rust Stop - Rustproofing Limitations

Limitations of Undercoating and Spray-on Rustproofing

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. 1.      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. 2.      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. 

Limitations of Capacitive Coupling Rustproofing

 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?

Even Cathodic Protection has its limitations

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 here


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