Simulated Service Tests

The most reliable performance data are obtained by field tests/surveys. One example would be to monitor and test the corrosion of autobody panels that sit in junkyards. Another example of in-service testing would be to monitor the behavior of the materials in a fleet of captive vehicles. This enables better control and recording of the exposure and driving conditions. The use of fleet vehicles also makes it possible to test coupons representing a larger database of materials. 

The most widely used simulated service test for static atmospheric testing is described in ASTM G 50, Practice for Conducting Atmospheric Corrosion Tests on Metals. It is used to test coated sheet steels for a variety of outdoor applications. Test materials, which are in the form of flat test panels mounted in a test rack (Fig. 16), are subjected to the cyclic effects of the weather, geographical influences, and bacteriological factors that cannot be realistically duplicated in the laboratory. Test durations can last from several months up to many years. Some zinc-coated steel specimens have undergone testing for more than 30 years. 

Acetic acid-salt spray ASTM G 85, A1 (formerly ASTM B 287) 

Copper-accelerated salt spray, or CASS (ASTM B 368) 

Acidified synthetic seawater testing or SWAAT (ASTM G 85, A3 formerly ASTM G 43) 

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Natural environmental exposure, the exposure of materials or products to natural environmental conditions, can be regarded as a form of simulated service testing. Such exposures provide information on the durability of the material without the effects of such factors as fatigue and abrasion. 

Estimates of service life are usually made either by natural or simulated trials or, most commonly, by accelerated tests with extrapolation to predict performance at longer times under less severe conditions. An alternative approach is to subject the product to environmental exposures which equate to the whole design life, and then to assess performance by real or simulated service tests (the end performance assessment). The exposures usually have to involve accelerated procedures and can be composed of several environmental agents applied simultaneously or sequentially. 

These standard tests do not cover all situations. Simulated service tests or in-service evaluations also need to be carried out. In-service tests should only be carried out if the potential for a positive result is very high or if requested by the customer. 

ASTM D 2394 Standard Method for Simulated Service Testing of Wood and Wood-Base Finish Flooring ... 

In 1930, Huey [4] described another simulated service test used at the Du Pont Co. since 1927 to quantitatively detect variations in the performance of iron-12 to 18 % chromium alloys intended for service in nitric acid plants. For rapid results, he selected a concentrated solution of 65 % nitric acid, which is near the constant boiling concentration of 68.5 %. Five 48-h periods, each with fresh acid solution, were proposed. Fresh solutions are needed to minimize the effect of corrosion products as described below. The weight... 

It was soon found that among the variables affecting corrosion rates were certain heat treatments that made not only the ferritic stainless steels subject to intergranular attack, but also the austenitic, 18Cr-8Ni alloys. From this simulated service test in boiling 65 % nitric acid, there evolved Practice C of ASTM A 262. Its large-scale use by one... 

Thus, the nitric acid test should be used primarily as a kind of simulated service test for alloys to be used in nitric acid environments. This is a return to its original function as defined by Huey [4]. When used in this way, it will be... 

The BNF or the VTR tests for visual carbon have been recognized as being unsatisfactory because these simulated service tests are not reproducible between laboratories and take far too long. Also, they do not diflierentiate between acceptable and unacceptable tube in borderline cases. 

Laboratory tests to determine the behavior of materials and corrosivity of automotive fluids such as engine coolants, engine oils, automatic transmission fluids, and fuels involve exposure to the actual fluid as close to operating conditions as possible. In most cases, aging of the fluids due to their functional use produces a more corrosive liquid therefore it is important that the test be conducted on used liquids or that aging of the fluid occur in-situ. Simple immersion tests can be used if chemical and physical environmental effects are introduced. This is not always possible and therefore simulated service tests have been developed. These laboratory bench tests simulate more... 

Standard Practices for Simulated Service Testing for Corrosion of Metallic Containment Materials for Use With Heat-Transfer Fluids in Solar Heating and Cooling Systems Standard Test Method for Corrosion of Steel by Sprayed Fire-Resistive Material (SFRM) Applied to Structural Members... 

Simulated Service Testing in the Plastics Industry, ASTM Spec. Tech. Pub. 375. 

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