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Superior corrosion protection

The majority of AVK products are as standard with internal and external epoxy coating according to DIN 30677-2 and GSK guidelines. The epoxy is applied manually or using a fluidized bed epoxy coating system. Prior to coating, all cast parts are blast cleaned to make sure that any unevenness is cleaned to provide perfect adhesion of the coating. The powder melts when in contact with the preheated components and cures when the components enter the cooling tunnel shortly after the coating process. AVK also offers gate valves with an external PUR coating, that is developed for use in steel gas pipelines with cathodic protection, but is also a good choice for installation in aggressive soils. Furthermore, we offer gate valves with a wear-resistant internal enamel lining. Enamelled valves offer excellent protection against creeping corrosion due to the chemical fusion of the lining and the ductile iron.

Thorough control measures are applied:
  • Layer thickness check

    The epoxy coating layer thickness is min. 250 my according to DIN 30677-2 and GSK requirements

  • Cross linkage test

    To detect possible imperfections in the epoxy coating, methyl isobutyl ketone is applied and wiped away with a cloth after 30 seconds.

    In order to pass the test, the cloth must not show any signs of coating.

  • Impact resistance test

    A stainless steel cylinder is dropped on the epoxy coating surface with an impact energy of 5 Nm. After the impact the component is electrically tested and no breakthrough shall occur.

  • Holiday detection

    A holiday detector with a brush electrode is used to reveal and locate any pores in the coating.

  • PUR layer thickness

    Layer thickness of PUR coating is of a minimum of 1.5 mm polyurethane.

  • Pinhole test of PUR coating

    Every single PUR coated valve is going through a high tension test of 20,000 V to make sure there are no pinholes.

  • Layer thickness of enamel coating

    The layer thickness must be 200 – 600 my according to DEV.

Photo of GSK coating



In addition to the above tests, the following tests are carried out when our coating process is monitored and approved by the independent GSK authorities several times per year:

Adhesion: The adhesion of the powder coating is tested on one plate for each coating plant four times a year using the punch separation method according to EN ISO 4624. The coating thickness over a dispersed area of the test plate shall be within the range 250 μm to 400 μm. The test plates are immersed for seven days in deionised water at 90ºC, and then dried in an oven for 3 hours. A conditioning phase of 3 to 5 days in normal atmosphere is then allowed to elapse. No blisters may arise during the period immersed in the water bath. The surface of the test piece is degreased and then roughened with abrasive paper. The roughened surface is cleaned from dust with oil-free compressed air and recleaned. The adhesion on the core side is tested with a minimum pulling force of >12 N/mm².

Cathodic disbonding: Cathodic disbonding tests are carried out on a test plate for each coating plant twice a year. For this test, the coating thickness over a dispersed area of the test item shall be within the range 250 μm to 600 μm. After the test it is important that no more than 10 mm of the coating can be peeled off.

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What is GSK?
The GSK Quality Assurance Association for Heavy-Duty Corrosion Protection of Valves and Fittings with Powder Coating (GSK e.V.) is the international industry network for businesses that coat valves and fittings with epoxy powder. GSK awards the RAL-GZ 662 Quality Mark (Gütezeichen) to companies who fulfil the strenuous quality-assurance requirements in accordance with the current Quality and Inspection Regulations. Click here for more information