Si-COAT 570 High Voltage Insulator Coating

The reliable, cost-effective, long term solution to pollution induced flashovers of high voltage insulators.

Insulator contamination has been a problem since the birth of electrical power distribution. Salt spray, industrial pollutants, and even desert sand can lead to costly power interruptions due to arcing and flashover.

While numerous attempts with other protective methods have had their limitations, there is a solution that utility maintenance engineers can rely on: Si-COAT 570 High Voltage Insulator Coating from Canadian Silicones Limited (CSL). The RTV silicone coating concept was developed in response to utility engineers requirements for long-term protection against pollution.

A long history of successful performance in highly contaminated areas has proven that CSL’s RTV silicone high voltage insulator coatings provides superior arcing and flashover protection in the most hostile environments. It lasts longer than other coatings and greases, providing significant savings in maintenance and replacement costs. One application of Si-COAT 570 generally leaves insulators virtually maintenance free for many years.

The problem with other “solutions”

Previous methods to protect insulators from flashover caused by pollution have included changes in insulator design to provide longer leakage paths and installation of conductive glazed insulators to ensure continuous surface-drying currents. Changing insulator specifications to provide longer leakage paths results in increased weight and higher initial costs. Although an improvement, these installations still require frequent washing or greasing in polluted areas. Conductive glazes often lose stability and increase losses through their consumption of electricity. The result is lower reliability, higher running costs and frequent insulator changes.

Frequent water washing or repeated applications of hydrophobic greases are also methods used to combat pollution. Water washing requires expensive equipment and has to be repeated frequently. The hydrophobic grease technique is labour intensive, messy and disliked by linemen. Neither of these methods provides the long-term protection expected by the modern utility maintenance engineer.

Si-COAT 570, high reliability, low lifetime running costs

To deliver the performance required by demanding maintenance engineers, Si-COAT 570 was formulated and put to the test globally by several major electrical utilities and many high voltage laboratories. It was found to resist corona, ultraviolet light, water erosion and the accumulation of airborne particle contamination.

During the last 30 years Si-COAT 570 has demonstrated its superiority in providing long term, maintenance free, flashover protection of high voltage insulators in polluted environments. The high performance of Si-COAT 570 is a direct result of its weather resistance and electrical characteristics. These special features include:

• Long-term water repellency/hydrophobicity. This is invaluable to high voltage applications because without it, contaminants on the surface of the insulators become wet and produce a conductive layer of ionisable material. This contributes to an increase in leakage current and probable flashover.
• Resistance to atmospheric and chemical degradation. The coated insulators remain unaffected by salt air, airborne pollutants, rain, humidity or ultraviolet light.
• Resistance to arcing and corona. Si-COAT 570 does not degrade to conductive by-products when exposed to electrical discharge.


A hydrophobic surface prevents water filming by forming discrete water droplets. The silicone oils in Si-COAT 570 transfer to the surface and coat contaminant particles which renders them hydrophobic. This reduces the contaminants ability to combine with water to form an ionic solution and interrupts the potential flashover mechanism at an early stage. Si-COAT 570 maintains these features over the long life of the installation and generally does not require cleaning or maintenance.

High reliability, long service means lower lifetime costs.

With Si-COAT 570, one application does it all – for years, eliminating the need for repeated water washing or greasing and this results in significant savings in maintenance and replacement costs. Time and again Si-COAT 570 has proven the long lasting, reliable and most economical solution.

Si-COAT 570 is supplied as a white or grey, one part room temperature vulcanising (RTV) silicone elastomer dispersion in a high flash point (40°C [104°F]) naphtha spirits solvent. The product adheres to glass and porcelain insulators and can be applied by spraying, brushing or dipping.

Recommendations on proper application, dilution techniques and spraying equipment are covered in the CCS Network HVIC application guide. Si-COAT 570 is normally applied in two to three coats depending on the type of spraying equipment being used. A 10 to 15 minute drying time between coats is required dependant on the temperature and humidity. All surfaces of the insulator should be coated with a cured thickness of between 0.38 and 0.50 mm (15 to 20 mil). The light colours allow visual inspection for uniform coating and the identification of thin spots. Porcelain and glass surfaces should be dry and clean before application.


· High viscosity which improves thickness build up and reduces slippage, drips and runs
High solids content which provides good value and limits weight loss from wet to fully cured
Optimal curing time parameters
Even suspension and dispersion of ATH
All of this results in a quality coating with fast application time

Long field-testing proves quality

For more than 30 years CSL customers have been using Si-COAT 570 throughout the world – from Argentina to Alaska, from Saudi Arabia to Singapore, and test sites such as these have proven that Si-COAT 570 is the superior coating. At many of the test sites, arcing and flashovers had been causing frequent outages – up to once a month. In most cases, once Si-COAT 570 was applied, arcing and flashover were eliminated.

Si-COAT 570– the superior coating

CSL believe that Si-COAT 570 is clearly superior. Only Si-COAT 570– with an unparalleled field application history can provide true peace of mind, long term, uninterrupted reliability and lowest life time running costs.

Prove it for yourself

We challenge you to complete an economic evaluation for your own specific situation. You’ll discover that Si-COAT 570 delivers more than just superior performance and better long-term economics. Why? Because Si-COAT 570 delivers long-life performance without the need for costly repeated maintenance procedures.

Please contact us for further information and product technical data