Humidity Cabinet Tests

In a humidity cabinet the humidity is raised to a value chosen as appropriate to the material under test. The temperature is generally cycled, so that the specimen is exposed to alternating humid air and condensation. 

The apparatus is automated to ensure that conditions are controlled within narrow limits. Other corrodent materials, such as sulfur dioxide, may also be introduced. Examples of humidity cabinet tests include ASTM D 2247 and ASTM G 85 listed in Table 5. 

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The CASS Test. In the copper-accelerated acetic acid salt spray (CASS) test (42), the positioning of the test surface is restricted to 15 2°, and the salt fog corrosivity is increased by increasing temperature and acidity, pH about 3.2, along with the addition of cupric chloride dihydrate. The CASS test is used extensively by the U.S. automobile industry for decorative nickel—chromium deposits, but is not common for other deposits or industries. Exposure cycle requirements are usually 22 hours, rarely more than 44 hours. Another corrosion test, now decreasing in use, for decorative nickel—chromium finishes is the Corrodkote test (43). This test utilizes a specific corrosive paste combined with a warm humidity cabinet test. Test cycles are usually 20 hours. 

D 1748 1983 Test method for rust protection by metal preservatives in the humidity cabinet... 

The relative aggressiveness of the environments proved to be consistent for all substrates, with the room temperature control the least hostile (virtually no loss of adhesion), and the cycle tests the most aggressive (up to 100% loss of adhesion within 60 days). Humidity cabinet exposure and 60°C water immersion yielded very similar values. As a result, for reasons of clarity, only water immersion data is actually presented here. Joint strength data obtained from either the Ford APG or Fisher Body Cycle Tests were identical, and were therefore also represented by one set of data points. The relative aggressiveness of the host environments toward... 

The rather more sophisticated injection type of humidity cabinet uses a humidity sensitive device to control the injection of moisture into the cabinet from a reservoir. Humidity levels are rather more easily controlled and changed with this type of apparatus and some types have the means to cycle both humidity and temperature in a prescribed manner, so extending the range of tests which can be carried out. 

After the introduction of combustion-modified polyurethane foam into the upholstery and bedding market, a wet compression set method, BS 4443, Part 7. Method 18, has become much more widely used. This is carried out by using a humidity cabinet set at 40 C and 95 100% relative humidity. Apart from recommending the use of a stainless steel compression apparatus, the only major difference from EN ISO 1856, 1996 is that the compression is carried out at 70% of the original thickness as opposed to the more normal 75%. This slight discrepancy arises becau.se of the original test methods devised by the automotive trade. 

Note Dynamic tests conducted in humidity cabinet having complete change of atmosphere every 3 minutes. Surface area to weight ratios of large Petri dish, small Petri dish, and vial were 17.0, 2.4, and 0.25, respectively. 

Cabinet tests consist in tests in which specimens are placed in a testing apparatus where the exposure conditions can be controlled. By means these tests it is possible to examine the performance of materials exposed to corrosive atmospheres that may be encountered in various locations, including near sea or in industrial areas. These tests can include the effects of humidity (RH), salt, corrosive gases (e.g. SO, H S, CO ), temperature and UV radiation. 

Strekalov and Berukshtis concluded that sea fog and warmth and humidity cabinets satisfactorily reproduce the nature of corrosive destruction of anodic coatings on steel, as observed under natural conditions in nonindustrial zones. Accelerated tests in SO2 gas cabinets were too harsh, however, and did not reliably reflect the behavior of zinc and cadmium coatings in a natural industrial atmosphere. 

Corrosion test cabinets have evolved from homemade water-and-spray tanks that operated at fixed or ambient temperatures and humidity to computer-controlled, multi-environmental laboratory apparatus that are not only functional, but are also an attractive addition to the laboratory. Sizes range from small benchtop units to large walk-in and drive-in chambers capable of testing hill vehicles or other large specimens. ISO requirements have led to the use of NIST traceable devices for measurement of temperature, humidity, and/or other critical conditions to enhance the accuracy and repeatability of the test conditions. A Ust of commonly used cabinet tests is shown in Table 1. 

Standard Test Method for Rust Protection by Metal Preservatives in the Humidity Cabinet... 

Cabinet tests are the most commonly used laboratory tests in the automobile industry. These have been developed to simulate the effects of atmospheric corrosion 44. Normally, a test chamber is used and the desired environment is introduced under controlled conditions. A list of these tests is given in Table 6. The simplest of these is the humidity test whereby the temperature and relative humidity within a chamber are controlled. A condensing humidity chamber, which operates at 100 % relative humidity and 38°C, provides... 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

Most cabinets incorporate a device whereby the test pieces can be sprayed with water at intervals for various periods of time with or without interrupting irradiation. Distilled water is normally used to avoid any effect of impurities. The humidity of the air between... 

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