Accelerated outdoor testing methods

This chapter describes the development of an outdoor certilication test program and subsequent efforts to create an accelerated weathering test method that could be used to predict the results of the outdoor protocol with a high degree of accuracy. Outdoor weathering tests were conducted in Florida, Arizona, and the northern temperate locations to obtain baseline data for comparison. This part of the research led to the development and subsequent publication of ASTM D6864. 

J.P. MOTan, P.R. Ziiiian, and M.W. Egbert, Cosmetic CoiTOsion of Painted Alumimun and Steel Automotive Body Sheet Results from Outdoor and Accelerated Laboratory Test Methods, Corrosion and Corrosion Control of Aluminum and Steel in Ughtweight Automotive Applicatbns, E.N. Soepenberg, Ed., NACE International, 1995, paper 374, p 374-1 to 374-22... 

Very light and weather resistant systems require very long outdoor exposure times. In order to accelerate the testing of pigmented systems, test methods have been developed which simulate outdoor conditions. The evaluation of such a test is not only conveniently accelerated, but the resulting data are easy to reproduce and independent of location, climate, date, and time. 

It might be interesting to note how far the results of accelerated test methods agree with full-length outdoor exposure and the effect of natural daylight. The correlation between outdoor or daylight exposure, including factors such as location,... 

There are various accelerated light stability test methods available and/or exposure in harsher climates (Florida, Arizona) to test the weathering performance. The prediction of photoageing stability based on accelerated laboratory testing is very difficult, but some attempts have been made for PVC-P (445). The most relevant point is to use as reference a formulation known to have good outdoor weathering performance. 

Test Methods. Tests for water repeUency of concrete and masonry have been described by several authors (72,94). The National Bureau of Standards (NBS) evaluated fifty-five clear water repeUents for masonry surfaces (95). Performance tests included water absorption, water-vapor transmission, resistance to efflorescence, change in appearance, and durability to accelerated and outdoor weathering. More recently, the National Cooperative Highway Research Program conducted a study of several organic and sihcone water-repeUent treatments. The results are communicated in Report 244 (96). The testing procedure used in this study is now a popular method for evaluating water-repeUent treatments on concrete. 

This practice describes the outdoor-accelerated-exposure testing of plastics and plastic-made products using Fresnel reflecting concentrator. The latter uses the sun as a source of UV and longer wavelength radiation and involves a system of plane mirrors focused on an air-cooled target board on which the test specimens are mounted. The three basic exposure methods are as follows ... 

Test method for failure end point in accelerated and outdoor... 

As an alternative to accelerated outdoor methods, laboratory equipment can be used which aims to reproduce, within a cabinet, the spectrum or part of the spectrum of natural sunlight combined with heating and/or moisture and/or darkness cycles. Test panels are exposed in such equipment which can then be run continuously. 

Association of Automobile Industries Working Group on Test Methods for Paints, Comparison of outdoor and accelerated exposure methods , J Coatings Technol 1986 58(734) 57-65. 

The described mechanisms of atmospheric corrosion demonstrate the importance of pollutants and of humidity cycles. Unfortunately, the complexity of the underlying phenomena, makes it difficult to predict atmospheric corrosion behavior Irom accelerated testing. Outdoor exposure tests, which generally require several years, therefore remain popular. Different norms and recommended practices fix in detail the conditions to be applied in atmospheric corrosion tests. The following accelerated test methods are most commonly used in the laboratory ... 

Accelerated test methods using artificial light sources reduce the time span of a test, but outdoor exposure is the only real means of obtaining reliable information. Most manufacturers use data based on trials in Florida, USA. Outdoor exposure data are reported in klloLangleys - a unit of energy irradiation (1 kLy = 1 kcal cm ). On average, 140 kLy relate to one year of exposure in Florida and 190 kLy to one year in Arizona. 

Accelerated outdoor weathering devices EMMA Test Method (ASTM G90-91)... 

Laboratory accelerated weathering tests have played an important role in development of polymeric materials with highly improved weatherability. However, since all stresses present in an outdoor exposure cannot be simulated in a laboratory accelerated test, the latter cannot replace natural exposure. It is a complimentary technique, the usefulness of which largely depends on how closely it reproduces the chemistry and weathering effects caused by the slower outdoor exposures. Thus, correlation is a fundamental issue which must be considered when selecting a laboratory accelerated weathering method. It depends on reasonably representing... 

The current salt spray test, in which the plated specimen is exposed to a spray or fog of sodium chloride solution, is the most widely used accelerated corrosion test for coatings, and various procedures have acceptance tests in standard specifications in numerous countries. Over the years, the procedure has employed sodium chloride solutions of concentrations between 3 and 20 %, sometimes with the addition of hydrochloric acid or hydrogen peroxide. The salt spray test [ASTM B 117, Test Method of Salt Spray (Fog) Testing] has largely fallen into disrepute because of the recognition that its reproducibility and correlation with outdoor exj>osure were often poor. Cyclic salt spray testing as well as alternate electrolytes such as the "prohesion test solution have been found to produce more realistic results. 

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