Corrosion Resistance

These tests are designed to evaluate how well the surface coatings protect substrates from corrosion. If you are more concerned with the effect of sunlight, moisture and temperature on the actual surface coating, please refer to our Durability tests.

The BS and ASTM standards mentioned here are copyright-protected documents and we are not able to provide you with copies. If required however, you can easily obtain copies from the British Standards Institution or the American Society for Testing and Materials.

Resistance to Cyclic Prohesion: BS 3900-F19, ISO 11997-2

Scope and Field of Application

BS 3900-F19 and ISO 11997-2 are alternative names for the same method which is intended to measure the resistance of coatings to a defined cycle of UV radiation and salt spray. The standard states that the test cycles specified have been found useful for testing air-drying industrial maintenance coatings on steel.

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

Summary of Method

The method involves the use of two different test chambers, one where the samples are exposed to UV radiation and the other where they are subjected to prohesion testing.

Cabinet Operating Conditions:

• Fluorescent Lamp Weatherometer; the chamber is fitted with UVA 340 nm lamps and set to repeat a test cycle consisting of 4 hours illumination at 60° C followed by 4 hours dark / wet at 50° C.
• Prohesion chamber this uses 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 samples are subjected to a cycle consisting of one week in the fluorescent lamp weatherometer followed by one week in the prohesion chamber. This cycle is repeated three times to give a total exposure time of six weeks (1,008 hours).

Sample Requirements

Ideally 150 x 75 mm coated (burnished steel) panels not more that 5 mm thick, although we can accommodate a limited number of 150 x 100 mm panels provided they are less than 5 mm thick. If you have smaller samples you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

The standard recommends running samples in triplicate.

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

Resistance to Cyclic Prohesion: ASTM D 5894

Scope and Field of Application

The ASTM D 5894 test method is similar to BS 3900-F19 : ISO 11997-2 in that both are intended to simulate the effect on coatings of exposure to a salt-laden atmosphere in the presence of sunlight

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

Summary of Method

This method is similar to BS 3900-F19 : ISO 11997-2 as Both methods involve the use of two different test chambers, one where the samples are exposed to UV radiation and the other where they are subjected to prohesion testing.

Sample Requirements

Ideally 150 x 75 mm coated (burnished steel) panels not more that 5 mm thick, although we can accommodate a limited number of 150 x 100 mm panels provided they are less than 5 mm thick. If you have smaller samples you can fix them to 150 x 75 mm panels provided the overall thickness does not exceed 5 mm.

The standard recommends running samples in triplicate.

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

Resistance to Cyclic Salt Spray: BS EN 60068-2-52, IEC 68-2-52

Scope and Field of Application

BS EN 60068-2-52 and IEC 68-2-52 are alternative names for the same method which is intended to measure how well components or equipment can withstand a salt-laden atmosphere. The method is designed to reproduce the corrosive effect of salt on metals where the mechanism is primarily electrochemical. It is also designed to reproduce the degradation of non-metallic materials by salt. In this case degradation is due to complex chemical reactions between salt and the materials involved.

We use this method mainly for testing electrical components and switchgear. If you need to test paints, coatings etc, you may wish to consider the prohesion test as a possible alternative.

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

Summary of Method

The method involves the use of two different test chambers one where the samples are exposed to salt spray and the other where they are stored under hot humid conditions. The salt spray uses a 5% aqueous solution of sodium chloride. The cabinet may be operated at any temperature between 15 and 35° C. The controlled temperature and humidity chamber is set to 40° C and 93% Relative Humidity

The test method enables samples to be tested to six different levels of severity. These are intended to replicate different service conditions . "Severity 1" for example corresponds to a marine environment in close proximity to the sea and would be appropriate for a sonar buoy or a ship's radar antenna. Severities 3 to 6 are intended for situations where there are frequent changes between salt-laden and dry atmospheres and are intended to replicate the use of vehicles on roads treated with salt during the winter months. Severities 3 to 6 include periods of storage outside the test chambers at 23° C and between 45 and 55% Relative Humidity.

Each level of severity is defined in terms of the time which the sample spends in each of the cabinets. In practice this involves alternating the sample between the salt spray and the controlled temperature / humidity cabinets with the option of storage periods at 23° C and between 45 and 55% Relative Humidity.

Sample Requirements

The size of any object we can test is limited by the capacity of the salt spray chamber. In practice this means that the test object must be capable of fitting inside a cube with 500 mm sides.

Resistance to Prohesion: ASTM G 85-94 Annex A5

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.

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.

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 need depends on the method of application. We will be pleased to advise you regarding our requirements.

Resistance to Salt Spray: BS 3900-F4

Scope and Field of Application

This standard gives an indication of how well a painted surface will resist artificial seawater spray.

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

Summary of Method

This method uses a mixture of salts, the proportions and concentration of which are chosen with the aim of producing artificial seawater. The chamber is operated at 20°C into which is introduced the aqueous solution of salt(s) in the form of a fine aerosol.

Sample Requirements

We require 3 coated panels 150 x 100 mm. The substrate should be the one that is appropriate to the type of paint being tested. We can test different size samples if required with maximum dimensions of 150 x 400 x 500 mm

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

Resistance to Salt Spray: BS 3900-F12, ISO 7253, BS EN ISO 9227, ASTM B 117

Scope and Field of Application

These tests give an indication of how well a painted surface will resist salt water spray. You may also wish to consider the prohesion test as a possible alternative. The prohesion test is a less severe version of the standard salt spray tests and is generally regarded as giving a better correlation with outdoor exposure results.

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

Summary of Method

BS 3900-F12 which is identical to ISO 7253 and virtually identical to BS EN ISO 9227 and ASTM B 117. This uses a 5% aqueous solution of sodium chloride. The cabinet is operated at 35°C

The methods involve mounting the test panels in a chamber into which is introduced an aqueous solution of salt(s) in the form of a fine aerosol. The methods vary according to cabinet temperature and the composition of the salt solution.

BS 3900 Part F 12 (and its equivalents) is the more severe method and the one that is most commonly used for paint testing. In our opinion, a system with moderate corrosion resistance can be exposed for 500 hours on a scribed test panel without developing any significant under-film corrosion. The best anti-corrosive systems currently available will offer this level of protection for exposure times in excess of 2,000 hours.

Sample Requirements

The requirements are the same for all the tests. We require 3 coated panels 150 x 100 mm. The substrate should be the one that is appropriate to the type of paint being tested. We can test different size samples if required with maximum dimensions of 500 x 500 x 500 mm

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

Resistance to Sulphur Dioxide: BS 3900-F8, BS EN ISO 3231 & ISO 3231

Scope and Field of Application

BS 3900-F8 is identical to BS EN ISO 3231 and ISO 3231 The tests are designed to measure the resistance of a coating to a humid atmosphere containing sulphur dioxide.

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

Summary of Method

The test panels are mounted in a cabinet above a heated aqueous solution of sulphur dioxide. Each test cycle consists of 8 hours exposure followed by 16 hours storage with the heater switched off and the cabinet open to the atmosphere.

The concentration of the solution is either 0.2 or 1.0 litre of sulphur dioxide in 2.0 litres of water. Other concentrations can be used if all parties agree. The temperature of the solution is 40°C and the total area of the panels under test should be 0.5 square metres.

The total surface area exposed is specified since it can affect the severity of the test. Increasing the surface area of test samples reduces the available sulphur dioxide per unit area and consequently reduces the severity of the test. The converse is also true.

The test panels are not normally scribed and, in our opinion, a coating with good sulphur dioxide resistance will show no apparent change or substrate corrosion after 10 cycles exposure to a 2.0 litre concentration. The best coatings currently available will provide this degree of protection for more than 20 cycles at this concentration.

The test is also used to measure the corrosion resistance of galvanised and plated metal items.

Sample Requirements

In order to obtain a total test area of 0.5 square metres, we require 16 coated panels 150 x 100 mm. The substrate should be one that is appropriate to the type of coating being tested.

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

Resistance to Sulphur Dioxide: DIN 50018

Scope and Field of Application

The DIN 50018 standard is similar to BS 3900-F8 in measuring the resistance of a coating to a humid sulphur dioxide atmosphere.

Summary of Method

The only differences between this test and BS 3900 Part F8 / BS EN ISO 3231 is that in the DIN 50018 test, the sulphur dioxide concentration is restricted to 1.0 or 2.0 litres and a calibration procedure is specified.

Sample Requirements

We require 16 coated panels 150 x 100 mm. The substrate should be one that is appropriate to the type of coating being tested.

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

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