The sulfidation process of sterling silver in different corrosive environments: impact of the process on the surface films formed and consequences for the conservation-restoration community

Heritage Science

Table 1 Identical sterling silver coupons with a polished surface were exposed to five different sulfidation environments. Based on the discoloration of the surface, the corrosive environments were arranged from slow to fast proceeding corrosion

	Slow corrosion process ⇔ Fast corrosion processes
Method no.	1	2	3	4	5
Environment	Indoor air	Indoor air	Gas	Gas	Liquid + aeration
Environment	Private residence	Laboratory	Gas	Gas	Liquid + aeration
Weathering conditions	Uncontrolled and variable conditions	Uncontrolled and variable conditions	Controlled and constant conditions	Controlled and constant conditions	Controlled and constant conditions
Corrosion procedure	Several coupons exposed to natural corrosion	Several coupons exposed to natural corrosion	Several coupons exposed to acid TAA gas atmosphere (NBN EN ISO 4538:1995)	Real-time corrosion in controlled relative humidity mixed with acidifying gases (H₂S, SO₂)	Several coupons immersed in alkaline 0.1 M Na₂S solution + aeration (NBN EN ISO 8891:2000)
Maximum exposure time	6 months	6 months	1 week	3 days	1 h