| Résumé : |
One of the most important pre-requisite for exterior automotive coatings is longevity. The ability to predict longevity, or service life, is key to developing new automotive coating technologies for the original equipment manufacturers (OEMs). While exposure testing is performed in natural field environments such as Florida, it is not cost or time efficient to solely use these results for automotive coating development.
Performance, as applied to paint systems, can be defined broadly as resistance to their environment, the latter covering all types of exposure conditions. In respect of the paint systems, the two most destructive influences are sunlight and moisture. The crucial test for any paint used on an exterior surface is the durability or resistance to an environment comprising weather and location. Weather consists of several factors - sunshine, rain, acid rain, temperature, fog, frost, atmospheric pollution and to a lesser extent wind. The influence of these weather factors on coated surfaces are studied in weathering tests. In order to speed up the product development process in automotive paint manufacturing industries, accelerated weathering tests are used to predict the longevity of the coating technologies in a fraction of the time that would be required for a field test. The acceleration factors can be as fast as 10 times, i.e., getting the equivalent of 10 years worth of field testing in one year of accelerated testing. There are a number of accelerated tests used, including QUV, salt spray, acid etch test, filiform corrosion, cyclic corrosion, weather-ometer (WOM), etc. Apart from these older tests, there are novel electrochemical methods such as electrochemical impedance spectroscopy (EIS) and electrochemical noise method (ENM). While there are many tests than can predict defects with good field correlation, there are other areas where correlation has been difficult. This review paper focuses on studying the various accelerated tests available till date and points, out their benefits and the improvements required so taht these accelerated tests resemble thenatural exposure effects. |
Aller sur edunet
Accueil
"Accelerated weathering". The need of OEMs in PAINTINDIA, Vol. LXII, N° 1 (01/2012)
