Question

Consider a scenario where steel is covered with a metallic gold coating with no scratches on the surface and steel unexposed. Explain the corrosion process.

Answer 1

The basic function of the electrically conductive surface of electrical contacts is electrical conduction. The electrical conductivity of contact materials can be largely reduced by corrosion and in order to avoid corrosion, protective coatings must be used. Another phenomenon that leads to increasing contact resistance is fretting corrosion. Fretting corrosion is the degradation mechanism of surface material, which causes increasing contact resistance. Fretting corrosion occurs when there is a relative movement between electrical contacts with surfaces of ignoble metal. Avoiding fretting corrosion is therefore extremely challenging in electronic devices with pluggable electrical connections. Gold is one of the most commonly used noble plating materials for high performance electrical contacts because of its high corrosion resistance and its good and stable electrical behavior.

Gold Coat is a revolutionary multi-layer protection system. It is comprised of an organic top coat barrier layer and a zinc layer placed over a steel substrate. This double barrier more effectively protects the steel from its environment.Gold Coat is specifically designed with corrosion inhibitors to address the electrochemical reactions of connector and fastener corrosion. Gold Coat is also uniquely formulated to be flexible, and an (pending) application process creates superior adhesion that bonds the Gold Coat to the galvanization. This provides for maximum durability throughout manufacturing, shipping, and installation.

Gold Coat barrier protection is provided from an organic coating. Types of organic coatings include resins, plastics, paints, enamels, and oils. The protective coating is an inert material that provides a physical barrier between the base metal and its surrounding environment. With this barrier in place, the metal will not react chemically and produce corrosion products. The metal cannot release electrons because the electrons cannot freely react to their environment.

Gold Coat is an excellent choice for most exterior applications. There are some environments which do not require the additional protection provided by Gold Coat. At the same time there are some environments which potentially need more protection than even Gold Coat provides.

In accelerated corrosion testing Gold Coat's weight loss was two to three times less than standard galvanization. Because of the inherent limitations of accelerated corrosion testing, and the numerous variables involved, such as real world environments and cyclic exposures, it is impossible to provide an exact anticipated performance life for Gold Coat.

Naturally we anticipate that during shipping or construction activity there will be some scratching of the Gold Coat surface. Because of the double layer protection, the underlying zinc layer will still provide protection for the base steel. USP has conducted corrosion testing on intentionally scratched samples to investigate its performance. By its nature, zinc has the ability to bridge across exposed areas and provide protection. This performance characteristic works the same way with Gold Coat connectors. However, using products with significant scratches should be avoided.