Resistance to Prohesion


ASTM G 85-94 Annex A5

prohesion test cabinet

Scope and Field of Application

This is a less severe version of the standard salt spray tests and is generally regarded as giving a better correlation with outdoor exposure results. The method involves mounting the test panels in a chamber into which is introduced an aqueous solution of salts in the form of a fine aerosol. The method differs from the standard salt spray tests in that the salt solution used in the prohesion test is much more dilute and the panels are not exposed to it continuously.

The test method was developed by British Rail and Mebon Paints and the term Prohesion is derived from a key concept of this development namely Protection is Adhesion.

Like all laboratory tests they have their advantages and limitations and these are summarised on our Testing Paints for Anti-Corrosive Properties page.

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

We also offer cyclic prohesion testing. This involves subjecting the samples sequentially to prohesion followed by accelerated weathering.

The actual standard is a copyright-protected documents 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

This method involves exposing the sample under test to an aqueous solution containing 0.05% sodium chloride and 0.35 % ammonium sulphate. The test cycle consists of 1 hour exposure to salt mist at ambient temperature followed by 1 hour drying at 35°C.

The test should be regarded as producing comparative rather than absolute data and ideally samples with known outdoor exposure performance should be used as controls.

Sample Requirements

We need 3 coated panels (150 x 100 mm). The substrate should be one that is appropriate to the type of paint being tested.

If you wish, we can prepare the test panels. The quantity of liquid paint we needs depends on the method of application. We will be pleased to advise you regarding our requirements.

 

Accreditation

PRA is accredited to ISO 17025 by the United Kingdom Accreditation Service (UKAS) to carry out this test.

Please contact Peter Collins for further details.

 

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