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JULY 2021 I SMT007 MAGAZINE 75 ing 100 mm thick; and atomic level deposition (ALD) coating 0.1 mm thick. ALD coatings are ultra-thin (1-200 nm), stochiometric, dense, and highly uniform in thickness. ALD process is performed in a vacuum reactor at relatively low temperatures typically 80-300°C depend- ing on the material deposited and the substrate thermal budget. To characterize/evaluate the conformal coatings, the corrosion rates of the coated thin films were measured and com- pared with uncoated (bare) thin films. glued on top of the conformal coatings in spaces between the serpentine thin films. e conformally coated thin-film setups were hung on the side walls of a modified iNEMI flowers of sulfur (FoS) chamber [10-13] and electrically connected to potentiostats through appro- priate electrical feedthroughs. e modified iNEMI FoS chamber is shown in Figure 2. e changes made to the chamber were the removal of the paddle wheel and the household bleach. As a result, there was no forced air circulation and no chlorine gas in the chamber. e corro- sive gas in the chamber consisted only of sulfur vapor. e sulfur concentration was 0.15 ppm when the chamber was at 40°C and 0.3 ppm when the chamber was at 50°C [14] . e rela- tive humidity in the chamber was controlled at 15% using ZnCl 2 saturated salt solution, at 31% using MgCl 2 saturated salt solution, or at 75% using NaCl saturated salt solution. e cham- ber air was not mechanically circulated as it had been in past projects on creep corrosion testing [10-13] . e resistances of the thin films were mea- sured using potentiostats to pump known val- ues of currents through the thin films and mea- suring the voltage drops across them. in film temperatures were monitored using thermo- couples attached to a data logger. Resistance and temperature readings were taken simul- taneously every 10 minutes over the 5.32-day period of each test. ree conformal coatings were tested: acrylic coating 39-45 mm thick; silicone coat- Figure 2: Flowers of sulfur chamber with the thin-film setup: a) Inside view of flowers of the sulfur chamber; b) sulfur and saturated salt trays; c) overall view. a) b) c) Figure 3: Psychrometric chart showing the four temperature-humidity test conditions.