Di-shield is a polyester co-polymer mixed with glassflake and other fillers to give excellent dielectric properties. Di-shield will cure at low temperatures, has excellent adhesion and is able to withstand the high pH generated in the vicinity, of impressed current and sacrificial anodes. Di-shield will continue to cure under water once applied, it requires no primer and is of buttery consistency to prevent slumping, whilst allowing ease of application at the required thickness.
This material was developed specifically to provide a dielectric shield in the area of impressed current and sacrificial anodes, for example on ships or other subsea structures where in the vicinity of the anodes you could have an increased current density/potential if there was any damage to the coating in the vicinity of the anode. This is essentially to reduce the risk of cathodic disbondment in those areas, in a similar ay to a cathodic disbondment test environment.
Cathodic Disbondment and Testing
Metal substrates are sometimes protected from corrosion using impressed current or sacrificial anodes. Cathodic disbondment is disbondment or delamination at a damage site, caused by the passage of the resultant voltage. The water is electrolysed to form hydroxyl ions at the substrate and on some coatings significant delamination can occur. Cathodic disbondment testing can be assessed in a laboratory most commonly by applying a known voltage across a plate with an artificial defect for a specified test period. There are various test methods used. The resistance of coatings to disbondment is a key factor in many applications and the ability to resist this effect is closely related to the immersed adhesive strength and the permeation resistance of the lining. Corrocoat’s glassflake filled linings have demonstrated excellent resistance to cathodic disbondment.
*Find out more on Cathodic Disbondment Testing – Anti Corrosion & Corrosion Protection Coatings by Corrocoat here.