[ODM]

It's interesting to look up topics regarding grounding rods and the factors affecting their conductivity. Sometimes the corrosion needs to be artificially strengthened to decrease resistance, with use of various salts of copper, or noncuprous salts which help the copper corrode faster.

This is purely an assumption, but if the conductivity of an earthing rod is improved by the leeching of copper corrosion products into the soil, which increases its contact area (in a perfect circular example, square of radius multiplied by pi) with the surrounding earth moisture, these conductive corrosion products will increase the apparent area of the target.

I'll dig up a document or two on this topic and post them, I remember coming across an article with a study on the topic but I won't be holding any claims until I can find a study backing them.