Flowers of sulfur tests

The simplest recommended technique is to identify any porosity of the coating as revealed by the presence of surface spots.

[1] Mixed flowing gas testing failed to alert the electronics manufacturing industry to weaknesses in immersion silver plating (for example, see Reference 7).

[2] The development of FOS testing for creep corrosion was furthered by efforts under the auspices of the International Electronics Manufacturing Initiative (INEMI) and the Surface Mount Technology Association (SMTA) by Haley Fu, et al.[3][4] and Prabjit Singh et al.[5][6] MFG testing also proved unreliable for high-sulfur environmental testing of chip resistors and their certification as sulfur resistant.

[7] The material under test is suspended inside a container over a source of powdered sulfur.

Humidity inside the container is typically controlled with a saturated salt solution whose vapor pressure is well characterized at the temperature of the test.

Porosity results are determined by the distribution, number and sizes of dark spots on the materials under test.

Again, the dark spots are due to reaction of the moist sulfur vapors with the underlying silver or copper material.

Vacuum desiccator bell jar with 316 stainless steel sample tree, dishes with flowers of sulfur and saturated potassium nitrate solution in the bottom.
Nominally 1 square centimeter silver coupon cleaned per ASTM B810-01a (Reapproved 2017) Cleaning Method I
Cleaned silver coupon exposed to flowers of sulfur for five days at 50 °C over saturated potassium nitrate solution (engraved with sample number).