What is a potential consequence of overheating a soldering iron?

Overheating a soldering iron can lead to damage to the tinned surface of the tip, making this the correct choice. The tinned surface is designed to allow for efficient heat transfer and protects the copper tip from oxidation and other forms of degradation. When the soldering iron is overheated, the high temperature can cause the tin plating to deteriorate, potentially exposing the copper beneath. This not only affects the iron's performance but also significantly shortens its lifespan, as unprotected copper is prone to oxidation and can become unusable over time.

In contrast, increased solder flow, enhanced tip lifespan, and improved melting speed are generally outcomes associated with optimal soldering conditions. However, these benefits do not hold true when the iron is subjected to excessive heat, which can compromise the integrity of the tool rather than improve its functionality.