High humidity testing

It is frequently desirable to test passivated parts to determine if the passivation has effectively removed free iron from machining operations. Both ASTM A 967 and ASTM A 380, Practice for Cleaning and Descaling Stainless Steel Parts, Equipment, and Systems, provide several methods to accomplish this. These include water immersion and high humidity tests which can be completed in as little as one day. 

An application for these new rare earth organophosphate corrosion inhibitors is as additives to epoxy coatings, where their low solubility makes them ideal for slow, controlled inhibitor release to stifle corrosion of coated substrates. Forsyth et showed that Ce(dbp)3 and CeCdpplj, when dispersed in a simple epoxy formulation and applied to AA2024-T3, could suppress the initiation and propagation of filiform corrosion in both alternate immersion and high humidity tests. 

There is also a differentiation between inside and outside parts. Outside parts have not only to pass high temperature and high humidity tests but also the corrosion test cycles like the VDA 621-415. Inside parts are exposed to higher temperatures (in some areas up to 120°C) than outside parts but are not exposed to a corrosive environment (O Table 46.1). 

The durability for a bonded system can be tested by applying cyclic loads on either simple lap shear specimens, more sophisitcated H-specimens or on the whole bonded structure (e.g., the whole car body). It is recommended to run a corrosion test or at least a high humidity test... 

The above-mentioned codes contain requirements for accelerated durabiUty tests. In addition, interlayer manufacturers and laminators expose test samples for several years under extreme weather conditions, eg, the Florida coast and Arizona desert. The laminated products weather extremely well, with no change in the plastic interlayer. Occasionally, clouding is noted around the edges when exposed to high humidity for long periods, but this is reversible. Colored areas of PVB laminates may fade while subjected to extensive uv/solar irradiation, which could cause an appearance issue. This has not, however, been shown to alter the laminate s other performance properties. 

These materials, when exposed to continuous high humidity, especially in the presence of an electrical field, hydrolyze into the acid and alcohol precursors from which they are made. The acid plus water present make a conductive material that will cause the material to short the electrical circuit. The process by which the decomposition of the TS polyester takes place is very gradual at first and then accelerates so that extended testing of the material is necessary to be sure that the particular polyester composition used is resistant to hydrolytic degradation. 

The moisture content of a plastic affects such conditions as electrical insulation resistance, dielectric losses, mechanical properties, dimensions, and appearances. The effect on the properties due to moisture content depends largely on the type of exposure (by immersion in water or by exposure to high humidity), the shape of the product, and the inherent behavior properties of the plastic material. The ultimate proof for tolerance of moisture in a product has to be a product test under extreme conditions of usage in which critical dimensions and needed properties are verified. Plastics with very low water-moisture absorption rates tend to have better dimensional stability. 

Xie J, Wood DL, More KL, Atanassov P, Borup RL. 2005a. Microstructural changes of membrane electrode assemblies during PEFC durability testing at high humidity conditions. J Electrochem Soc 152 A1011-A1020. 

Borup et al. [254,255,258] have studied the corrosion of DLs. They aged different types of hydrophobic treated DLs for around 1,000 hours in deionized water at 80°C. After these aging tests, the samples were fuel cell tested at different relative humidities. It was observed that the DLs that were aged behaved like hydrophilic DLs they showed the best performance under dry conditions and the worst under high-humidity conditions due to flooding. On the other hand, hydrophobic DL materials that were not aged showed the lowest performance during dry conditions and the best... 

Hydration Resistance. Visual examination of a series of Inhibitor-treated FPL-prepared 7075-T6 A1 coupons exposed to high humidity conditions for specified time Intervals Indicated good short-term hydration resistance for several phosphonate and silane compounds (no visible discoloration) The most effective silane compound tested contained the mercapto (-SH) functional group. 

Imide passivated linear devices was determined from I-V characteristics of statistically significant numbers of devices following severe PTHB test (i.e., 15 psi, 120°C, 100% relative hvimidity, and 30 V bias). Two coat (3 p) polyimide passivation provided almost twice the mean time to failure of 1 p thick PSG passivation. Polyimide protection against high humidity (13,14) and Na" " diffusion (15) has been reported previously. 

These results strongly indicate that DSSCs show sufficient physical and chemical stability during extended periods of illumination. Nevertheless, stability tests at high temperatures and high humidity must be carried out for outdoor applications. 

As described in Section V, A. 2, satisfactory long-term stability of sealed cells has been already achieved under relatively mild test conditions (low temperatures and no UV exposure). For outdoor applications, additional stability tests under more rigorous conditions will be required (e.g., high temperature such as 80°C, high humidity in the atmosphere, and UV exposure). 

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