Cyclic Corrosion test (CCT) started as per international standards

April 12, 2012 - PRLog -- Spectro has introduced the more reliable ‘Cyclic Corrosion Test’ for better prediction of the behavior of test components (especially towards corrosion) exposed to natural cyclic conditions.

Both the ‘Cyclic Corrosion test’ and the long used ‘Salt Spray test’ are accelerated Corrosion tests that determine the behavior of materials in response to aggravated parameters like temperature, humidity, concentration of corrosive species like ionic contaminants, in a fraction of the real life time. But the results obtained from ‘Salt Spray’ tests are often misleading or less realistic in comparison to those obtained by the ‘Cyclic Corrosion’ test. This is because the ‘Salt Spray’ test suffers from the inherent flaw in its test design, i.e. same/fixed experimental parameters mentioned above,  which are not made to change over a time period. This creates an incompatibility between its own generated corrosion mechanisms and the actual corrosion mechanism that takes place in real life situations. On the other hand, with ‘Cyclic Corrosion’ testing, the parameters are periodically changed over a time period, for e.g. 24 hours, so that this method simulates the natural cyclic conditions in a better manner. Hence, the data/results obtained from CCT testing are more reliable in predicting the lifetime of a test component than the ‘Salt Spray’ test. The results/data from these tests are used as inputs for Quality Control in a number of industries manufacturing automobiles, appliances, aviation, electrical and military components etc.
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Cyclic corrosion testing is intended to produce failures representative of the type found in outdoor corrosive environments. CCT tests expose specimens to a series of different
environments in a repetitive cycle. Simple exposures like Prohesion may consist of cycling between salt fog and dry conditions. More sophisticated automotive methods call for multistep cycles that may incorporate immersion, humidity, condensation, along with salt fog and dry-off.

Any or all of the following environments may be used for Cyclic Corrosion testing:-
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1. Ambient Environment:  As used in CCT procedures this term means laboratory ambient conditions. Ambient environments are usually used as a way to very slowly change the test sample’s condition.

2. Chamber Environments:  Non-ambient environments are usually chamber exposures. Cycling between different non-ambient environments can be performed by physically moving the test specimens from one chamber to another or, in automated chambers, by cycling from one condition to another.

3. Fog (Spray) Environment:  Salt fog application can take place in a B117 type test chamber or be done manually in a laboratory’s ambient environment. The fog nozzle should be such that the solution is atomized into a fog or mist. Commonly, in addition to NaCl, the electrolyte solution contains other chemicals to simulate acid rain or other industrial corrosives.

4. Humid Environment:  CCT procedures often call for high humidity environments. Typically they specify 95 to 100% RH. These may be achieved by using ASTM D 2247. As an alternative, a B 117 chamber may sometimes be used to apply a pure water fog.

5. Dry-Off Environment: A dry-off environment may be achieved in an open laboratory or inside a chamber. The area should be maintained with enough air circulation to avoid stratification and to allow drying of the material. The definition of “dry-off” can be ambiguous. There is disagreement on whether a specimen should be considered dry
when the surface is dry, or when the specimen has dried throughout. As corrosion products build up, the time necessary to achieve full dry-off may increase.

6. Corrosive Immersion Environment:  This environment would normally consist of an aqueous solution with an electrolyte at a specified concentration, typically up to 5%. Typical pH is 4 to 8 and temperature is usually specified. The solution should be changed on a regular basis as it becomes contaminated with use.
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7. Water Immersion Environment: Distilled or de-ionized water should be used. ASTM D 1193 provides useful guidance on water purity. The immersion container should be made of plastic or any other inert material. Acidity of the bath should be within a pH range of 6 to 8. Temperature should be 24°C ±3°C. Conductivity should be < 50 mmho/
cm at 25°C