Accelerated Laboratory Test

Recent interest in weathering steels has stimulated work on accelerated laboratory tests which can be used to investigate the effect of alloy composition on performance. It is well established that a wetting and drying cycle should be an integral part of any laboratory test in which the characteristic properties of weathering steels are revealed , and Bromley, Kilcullen and... 

Many accelerated laboratory tests have been devised to determine the susceptibility of paint films to breakdown by atmospheric weathering, however, the demand for a generally applicable test exists. In this study different typical paint systems have been subjected to various natural environments and laboratory tests (DEF-1053 Method No. 26,... 

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. 

A comparative investigation of MIOs with different shapes, i.e. granular or a more lamellar shape (carried out within a study for the Deutsche Bahn AG ) has shown no difference in the application of either grade in protective coatings with regard to the anticorrosive effect. This has been confirmed not only by accelerated laboratory tests but also by means of outdoor exposure in a coastal climate [5.103]. 

On the basis of this evidence, it is recommended that an experimental test program, consisting of both laboratory and field tests, be developed and Implemented to quantitatively measure the effects of acid deposition on both the as thetic and structural properties of PCC structures. It is, however, recommended that a preliminary series of controlled, accelerated laboratory tests be carried out before a full-scale field evaluation program is instituted. The objectives of the accelerated laboratory test program should be to identify the magnitude of the problem and to attempt to differentiate between the effects of wet deposition, dry deposition, and normal weathering. The preliminary test program should concentrate on surface chemistry effects and penetration rates of SO4, NOx, Cl as deposited from wet and dry deposition. The... 

It is now well established that wear of rubber is not a purely mechanical failure process in that it contains a contribution due to thermal-oxidative breakdown of the polymer (226—228). Still, under severe conditions, which apply to all accelerated laboratory tests as well as to many situations encountered in tire wear, abrasion is dominated by tearing processes. 

P.E. Manning, Comparison of Several Accelerated Laboratory Tests for the Determination of Localized Corrosion Resistance of High-Performance Alloys, Corrosion, Vol 39, 1983, p 98-102... 

Generally poor correlation between accelerated laboratory test data and the natural outdoor exposure. 

ASTM D 2017 Standard Method of Accelerated Laboratory Test of Natural Decay Resistance of Woods (Discontinued)... 

Temperature or humidity fluctuations can be accelerated only to the point of maintaining uniform penetration that is likely in the end use environment. If creep or vibration is expected in service, time-temperature superposition may often be applied to accelerate laboratory testing. This technique mathematically predicts the material s response in service, based on laboratory characterization of the material over a... 

An alkyd resin containing less than 1% PANI was examined for its ability to protect carbon steel against aqueous corrosion. In field tests, in urban and marine environments, as well as in accelerated laboratory tests, the presence of PANI in the alkyd resin improved the corrosion protection of carbon steel and also the degradation resistance of the coating [214]. 

Information on the natural weathering behaviour of joints is very useful. By combining this information with data from accelerated laboratory tests, some realistic predictions of service-lifetime may be made. Theoretical models of the pattern of bondline saturation of joints as a function of time of environmental exposure provide a useful appreciation of the possible extent of problems (e.g. Fig. 4.21). The process of joint failure, as observed in practice or in the laboratory, is frequently non-diagnostic i.e. it rarely reveals the true cause, or the series of stages, leading to deterioration or failure. 

Table 2.13 Plan for accelerated laboratory tests of panels ...

Various accelerated laboratory tests were conducted on both uncoated and coated MS and WS panels. 

It was tried to recreate the parameters of field tests at the accelerated laboratory tests where the effect of humidity, chloride ions and presence of SO2 were considered. Comparison of Table 3.22 (lab test) and 3.3 (field test) reveals that the corrosion rate of as received MS and WS in 3.5 % NaCl is lower than the exposed panels. Eaya of as received panels are also greater. However, corrosion rate in cyclic polarisation of MS and WS after SO2 exposure is comparable to cyclic polarisation of coated panels after 18 m exposed at P3 as can be seen from Tables 3.23 and 3.4 and Figs. 3.39 and 3.8. Both plots show passivity. In general, the trend WS is more corrosion resistant than MS as seen in both field and laboratory tests. 

Corrosion rate of weathering steels was found lower with respect to mild steels in accelerated laboratory tests. They corrode most rapidly with respect to field exposure test... 

The data generated with accelerated laboratory tests on both coated and uncoated mild steels and weathering steels are grossly insufficient to predict field behaviour. 

Present research work has been carried out in two parts field exposme tests and accelerated laboratory tests on unexposed panels. Under field exposme test three representative sites PI very close to sea shore and free firom SO2, P2 away from sea with presence of SO2 and P3 industrial environment with presence SO2 were chosen. Analytical techniques (EDX, XRD and Raman spectroscopy) were used for rust characterisation and SEM was employed for understanding the morphological state. Corrosion rates were estimated after different periods of exposure at sites. It is found that though accelerated laboratory test can predict the general trend of corrosion, actual field test data cannot be created in laboratory. So an attempt was made to simulate protective rust coating in the laboratory that is typical of field exposure protective rust formation on weathering steel. 

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