What does a passive film do to prevent further corrosion?

A passive film serves as a protective layer that effectively acts as a barrier on the surface of a metal. This barrier prevents corrosive substances, such as moisture and salts, from reaching the underlying metal. By hindering the direct contact with these corrosive elements, the passive film significantly reduces the rate at which corrosion can occur.

The presence of this film is crucial because it ensures that even if some areas of it are compromised, there may be enough of this protective layer remaining to continue safeguarding the metal from corrosion. This characteristic is fundamental to the longevity and durability of materials, especially in environments that are prone to corrosion, such as marine settings.

In contrast, the other options describe processes that would either allow corrosion to occur or do not contribute positively to corrosion prevention, highlighting the importance of the passive film's role in maintaining the integrity of metal surfaces.