Chemical failure

Survey capability with ppm detection limits, not affected by surface charging effects complete elemental coverage survey microanalysis of contaminated areas, chemical failure analysis... 

Another section of TSCA requires the manufacturer to notify EPA if there is any indication of substantial risk from any chemical. Failure to do so by the manufacturer within a specified time period may result in civil penalties or possibly criminal prosecution. 

Major causes for coating failure are surface cracking and undetected pinholes or voids. These can be repaired and serious problems avoided. Coatings generally fail in different modes, these are chemical failure, abrasion failure, adhesive failure, cohesive failure and undercoat corrosion. For performance evaluation of coatings on experimental basis on these parameters various ASTM and BS specifications are presently being used. 

Using loss in reflectance as an indication of mirror failure and change in tensile properties as an Indication of polymer failure, we can rank the polymer/mirror assemblies studied for overall performance. In Table I we rank all the assemblies in terms of poor, intermediate, and good performance. FEK-244 or PMMA(3M)/Al/adhesive is the most durable of the polymer/mirror combinations studied. Poor performers warrant no further study. Intermediate cases show some promise and could possibly be improved with modification of the polymer/mirror assembly. Both physical and chemical failure have been observed in the pol3raier-... 

Chemical failure of quite a different type was observed for... 

Use of a reagent or carrier that is badly prepared, incorrectly labeled, inappropriate to the method, or no longer effective, can be pinpointed by first repeating the analysis with a completely different set of reagents and, if successful, then checking each original reagent in turn. In tandem with chemical failure. 

Racheli But the Fukushima disaster was not really a chemical failure. 

Radiation failures are principally caused by uranium and thorium contaminants and secondary cosmic rays. Radiation can cause wearout, aging, embrittlement of materials, or overstress soft errors in such electronic hardware as logic chips. Chemical failures occur in adverse chemical environments that result in corrosion, oxidation, or ionic surface dendritic growth. There may also be interactions between different types of stresses. For example, metal migration maybe accelerated in the presence of chemical contaminants and composition gradients and a thermal load can accelerate the failure mechanism due to a thermal expansion mismatch. 

PCB faUirre mechanisms fall into three gronps thermally indnced faUnres, of which plated-throngh-holes are the most important example mechanical failnres and chemical failure mechanisms, of which dendritic growth is the most important example. 

A mechanical failure, for example, could occur as the result of an impact between a ship and another moving vessel or a stationery object. An electrical failure could occur as the result of internal partial discharges that degraded the insulation of a ship s propulsion motor. A chemical failure could occur as the result of corrosion of poorly protected parts/components on an offshore wind turbine. Finally, a thermal failure could be the result of heat generated by current flowing in an electrical conductor, causing insulation degradation. 

J. R. Nicholls, R. Newton, M. J. Bennett, H. E. Evans, H. Al-Badairy, G. J. Tatlock, D. Naumenko, W. J. Quadakkers, G. Strehl, and G. Borchardt. Development of a Life Prediction Model for the Chemical Failure of FeCrAl(RE) Alloys in Oxidising Environments. In M. Schtltze, W. J. Quadakkers, and J. R. Nicholls. (eds). Lifetime Modelling of High Temperature Corrosion Processes, pp. 83-106, London, 2001. European Federation of Corrosion, lOM Communications. EFC Publication No. 34. 

Schematic representation of the oxidation induced chemical failure of FeCrAlRE alloys. 

In the corresponding tests on aluminised (8 wt.% Al), 1 mm thick, Aluchrom YHf and Kanthal AF sheets, the aluminised alloys oxidised at slightly faster rates than the as-fabricated alloys at 1200°C (Fig. 8.14). However, although the exposures were 3000 h, these were much shorter than the time needed to establish whether the increased Al alloy content affected the time to breakaway, e.g. the lifetime of 1 nun Kanthal AF sheet at 1200°C was 13,000 h [3]. At 1300 C, in contrast, the increased Al content reduced the oxidation rate of Kanthal AF (Fig. 8.16), so that whereas the lifetime of the as-fabricated alloy was 1300 h [3], chemical failure of the aluminised Kanthal AF did not occur during the current exposure (3000 h). Aluminising Aluchrom YHf to 8 wt.% Al had no influence on the oxidation rate (Fig. 8.16). However, at both temperatures aluminising enhanced the spallation propensity of both alloys (Figs 8.15 and 8.17). 

Based on current understanding of temperature dependence, the mechanisms of scale growth and scale compositions and also of the two-stage, oxidation induced chemical failure process of FeCrAIRE alloys, the development and evaluation of two potential procedures to increase alloy lifetimes have been major objectives of the CEC SMILER project. The majority of testing has been undertaken in laboratory air, as described in this chapter but has been substantiated by concurrent evaluation in other simulated relevant industrial environments [26]. The procedures involved first increasing the alloy A1 reservoir, and second gas annealing prior to service to pre-form a stable a-AI2O3 protective scale and also to remove possible deleterious non-metallic alloy impurities, such as sulphur. 

Schematic of the different possible types of Cr depletion kinetics in an alloy and consequences on the protective effect of the scale. (1) Uncritical. (2) Potential chemical-mechanical failure with repassivation. (3) Potential chemical-mechanical failure without repassivation. (4) True chemical failure.

After the tests concluded the parts were examined for chemical failure resulting in discoloration or stress cracking. The results of the filled and imfilled materials were compared to determine the levels of effects the active packaging additive had on the chemical resistance of stress induced parts. 

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