ASTM B808-10 (2020) pdf free

04-10-2021 comment

ASTM B808-10 (2020) pdf free.Standard Test Method for Monitoring of Atmospheric Corrosion Chambers by QuartzCrystal Microbalances.
Corrosion film growth with thicknesses varying from amonolayer of atoms up to 1 um can readily be measured on acontinuous, real-time,in-situ, basis with QCMs.The test results obtained for this test method areinfluenced by various factors,including geometrical effects,temperature, humidity, film thickness, film materials,electrodeconditions,gases in the corrosion chamber,atmosphericpressure,and so forth. Calibration of coated crystals andinstrumentation and reproducible crystal operating conditionsare necessary for consistent results.
After metallization of the crystals, they should be storedin desiccators.After two years storage or if the metallizationshows discoloration or staining, the crystals shall be discarded.Crystal surfaces should not be chemically or mechanicallycleaned before use in the corrosion chamber. They should beblown clean with inert compressed gas.Chilling and conden-sation on the surface, as can occur with the use of pressurizedfluorocarbons, shall be avoided.Care shall be exercised so thatthe crystals are only handled by clean tweezers or tongs andnever touched by hands.
QCMs and its electronics shall be calibrated initially ina given corrosion system and thereafter on an annual basis.Calibration shall be performed with the same shape and size ofcrystal holder to be used during operation. Recalibration shallbe performed if the crystal holder geometry is changed.
All metal surfaces that are not being used in themeasurement should be shrouded or coated with a nonreactivematerial to protect the surfaces from unwanted corrosion (thatis, clear nail polish,Q-dope, heat shrink TFE-fluorocarbon, andso forth). It is especially important to protect any electricalconnections that are being used for measurements or providingpower from the corrosive atmosphere under investigation.8.2 Do not handle the crystals by hand or with anything thatleaves a residue after evaporation on the crystal electrodes. Usecaution in all handling to avoid scratching the sensing filmsurface. One QCM with a sensing film inert to the test environ-ment should be in the system to monitor changes in the amountof relative humidity in the system, adsorbed hydrocarbons, andso forth.(A gold-coated QCM is usually a good choice for thisapplication.) At the end of the chamber exposure when all thepollutant gases have been removed and the humidity has beenreturned to its initial value, the frequency of this QCM shouldstill be at its initial value. (This is not meant to replace arelative humidity meter, rather it verifies the system electronicsstability.)ASTM B808 pdf download.

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