Electrochemistry of corrosion

Question

Co on Ag noble or sacrificial coating and why

Answer 1

Checking the activity series of metals, one finds that Co is more reactive than Ag. Therefore, in this case,

Co on Ag would represent a sacrificial coating. The main difference between a noble and sacrificial coating is the following:

sacrificial = coating is more reactive than the metal being coated so it will corrode first

noble = coating is less reactive than the metal being coated so as long as it remains intact, it protect the substrate metal.