What is the major problem of pitting corrosion on carbon steel equipement?

The major problem for pitting is the corrosive media/environment. Pitting generally causes because of crevice  corrosion within the material. The best way to hinder pitting is to completely isolate substrate from corrosive media.

localized loss of thickness may occur on the surface of equipment,that is holes or cavities may be formed.these cavites are also called corrosion pits .they act as stress raisers and can lead to fatigue corrosion and stress corrosion cracking .

in a condensor , the tubes inside the shell may be the victim of pitting corrosion.fully penetrating holes may even be formed due to pitting.the shell surface and baffle plates are also prone to corrosion.