Soon after Harbor Towers in Boston was built in 1972, residents complained about water leaking into their units. Over the next several years, saltwater from winds coming off the sea penetrated the porous concrete and corroded the steel reinforcement. Carbonization reduced the alkalinity of the concrete surrounding the steel, making the condition even worse. The concrete began to crack and scale. Freeze/thaw action accelerated the process and made the building unsafe. The homeowners' association authorized $10 million to complete repairs.

Of the 30,000 patches installed, only 30 failed during the final test of the construction phase and had to be replaced. No patches show evidence of having lost their bond since that time, and it's difficult even to locate the patch sites.

Precautions paid off because 4 years later there is no evidence of scaling or peeling. The coatings are preventing penetration of water and chlorides into the concrete—keeping steel reinforcement from further deterioration.