Which type of atmospheric corrosion occurs at a relative humidity of 70% or higher?

In the context of atmospheric corrosion, damp corrosion is the appropriate term for corrosion that occurs at relative humidity levels of 70% or higher. At these humidity levels, moisture in the air creates a conducive environment for corrosion to develop, as water can form a thin film on metal surfaces. This moisture facilitates the electrochemical processes that lead to corrosion, making the metal susceptible to oxidation and other deterioration processes.

Damp corrosion can be particularly problematic as it involves both oxygen and moisture, leading to more aggressive corrosion compared to dry conditions. In contrast, dry corrosion occurs in lower humidity levels where moisture is not present to facilitate the corrosion reaction. Wet corrosion would suggest significant liquid water contact, while electrolytic corrosion typically refers to corrosion that occurs due to electrochemical processes influenced by electric currents, rather than just atmospheric humidity.

Thus, understanding that damp corrosion directly relates to elevated humidity conditions helps in recognizing its significance in the study of corrosion and metal degradation.