Si-COAT® 570™ High Voltage Insulator Coating

Si-COAT (570) HVIC is a one-part, room temperature vulcanizing (RTV) polysiloxane (silicone) coating. Its unique and patented formulation provides a highly hydrophobic surface for its entire life, which virtually eliminates leakage current on high voltage insulators.

  1. Superior retention of hydrophobicity, ensuring a tremendously long life span
  2. A more robust self-cooling mechanism to protect the surface from physical damage in the case of dry band arcing.
  3. Supplied ready-to-use without the need of additional thinning or excessive mixing/shaking before use.
  4. The coating is not affected by UV light, corona discharge, soluble and non-soluble contaminants, airborne chemicals,salt, extreme temperatures or corrosive environments. Thus, Si-COAT HVIC is suitable for use in almost any service environment.
  5. Unlike the silicones used in composite (polymeric) insulators, no heat is required to cure Si-COAT HVIC. This means the free fluid (LMWS) in the coating is not subject to further reactions during the curing process. Thus, more free fluid is available under actual field service, which dramatically enhances coating performance.
  6. Over 25 years of succesfull application history.
  • Si-COAT eliminates the need for repetitive maintenance of
    contaminated insulators with directly measurable benefits:

    • Reduced maintenance expenses
    • Increased system reliability and efficiency
    • Increased revenue potential
    • Reduced environmental impact
Patented Technology
The basis of the Si-COAT 570 is the optimally-sized alumina trihydrate (ATH) particle and the optimum concentration of the ATH ingredient, discovered by the engineers and chemists at CSL Silicones Inc. The presence of ATH in the formulation of the HVIC is necessary to protect the coating from the damaging effects of tracking under electrical activity along the surface of the coating. (surface discharges should occur under adverse conditions)
It is essential that the ATH particle be optimally-sized and in an optimum concentration in order to promote long-term hydrophobicity of the coating.The 13-micron metal hydrate particle employed in Si-COAT HVIC balances the need for maximized metal hydrate surface area with the need for a free flow of essential low molecular weight siloxane (LMWS) to the coating’s surface.
Some low-quality products exclude the ATH and replace it with very inexpensive quartzfillers. While quartz-filled product is promoted as the latest generation of technology, do not be fooled. ATH is essential. The Si-COAT HVIC patent is based on the discovery that the optimum size of ATH is 13-microns.
The purpose of the ATH is to protect the silicone in case.
Without ATH, the silicone may burn. Protection is provided by the surface of the ATH particle. On a per unit mass basis, the surface area of ATH is increased by making the particles smaller in size.
However, small ATH will clog the pathways within the coating through which the LMWS must diffuse in order to reach the coating surface.
LMWS must be allowed to freely & rapidly diffuse through the body of the coating in order to quickly microencapsulate contamination as pollutes the insulator surface. Through deep research & testing it was determined by the laboratories of CSL Silicones Inc. that the optimum ATH particle size is 13-microns.

How Si-COAT HVIC Prevents Leakage Current

Coating the insulator with Si-COAT HVIC eliminates leakage current. The coating secretes a monolayer of LMWS. LMWS can be thought of as an oil. LMWS: very low surface energy + very high dielectric strength. As contamination particles come to rest on the surface of the coating, they come in direct contact with the microscopic LMWS. Within a few minutes the contamination particles become microencapsulated by the LMWS. This is possible due to the very low surface energy characteristic of the LMWS. Water that may collect on the surface is physically and electrically isolated from the contamination particles. Electrical isolation is by virtue of the very high dielectric strength of the LMWS. Further, the water forms in discrete droplets due to the very low surface energy of the LMWS. This is known as hydrophobicity. The elimination of water filming further discourages leakage current.

The phenomenon described above provides very long term protection. The long service life of Si-COAT has been conclusively demonstrated on millions of insulators installed across the globe since 1987. Si-COAT affords such long term reliability due to its rich and dense reserves of LMWS. Further, the unique and patented formula ensures LMWS migration to the coating surface remains unimpeded.
Unsurpassed Performance Phenomena

In most cases, Si-COAT achieves ultra-hydrophobity, which is an extreme contact angle greater than 150∘. The abundance of LMWS in Si-COAT combined with contamination particles creates a hydrophobic microtexture on the surface of the coating. Science has named this phenomenon the “Lotus Leaf Effect”. As on a lotus leaf, water simply rolls away and vanishes.
Because Si-COAT HVIC develops ultra-hydrophobicitythe coating has a tendency to remain dry by quickly shedding off water. An insulator that remains dry is an insulator that remains at its highest insulating performance.
Si-COAT HVIC is suitable for use on overhead transmission & distributions lines and in substations.

Si-COAT is also suitable for use at all voltage levels including the latest UHV projects.
 Installations in service for over 25 years continue their outstanding performance, saving the end-user maintenance expenses and reliability concerns. According to one European utility, the cost to apply Si-COAT in their switchyards is recovered within a year due to the savings from eliminating water washing and the avoidance of expenses related to outages. By virtue of its ability to nearly eliminate all leakage current, Si-COAT has achieved remarkable results in very harsh conditions around the world. Consultation by CSL Silicones Inc. has helped utilities from far corners all over the world recover losses in ways no other insulating technology can.
Si-COAT HVIC: The world’s best RTV Silicone HVIC Patented Technology