Wet Adhesion

ASTM D 6900

 Wet Adhesion

Scope and Field of Application

Exposure of applied coatings to wet or humid conditions may lead to loss of adhesion to the substrates over which they have been applied. Water based coatings, especially ones that have been recently applied, may be moisture-sensitive and prone to this mode of failure.

ASTM D 6900 is a method of quantifying the adhesion of emulsion paints to glossy surfaces under wet conditions.

There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.

The actual standard is a copyright-protected document and we are not able to provide you with copies. If required however, you can easily obtain copies from the American Society for Testing and Materials.

 

Summary of Method

The method involves applying the test paint to a film of cured alkyd gloss paint on a plastic substrate. The test paint is then allowed to dry for an agreed period of time under standard temperature and humidity conditions.

The standard defines how a lattice pattern (consisting of one set of six cuts and one set of ten cuts at right angles to each other) should be cut through the test paint film. This reduces the paint film within the lattice to 160 small squares of coating. The standard defines the spacing of the cuts and hence the size of the squares.

The test piece is then immersed in water for 30 minutes, assessed for blistering (we use the BS 3900-H2 : ISO 4628/2 method) and then scrub tested according to ASTM D 2486.

The number of cycles required to produce 100% adhesion failure is recorded. If this does not occur by 500 cycles, the test is terminated and the percentage adhesion failure at 500 cycles is noted.

 

Sample Requirements

We require 1 litre of coating.

 

Accreditation

Although PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS), we are not accredited to carry out this particular test.

 

 

Please contact Peter Collins for further details.

 

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