Pictures show roofs 25+ years old

• Field experience of unpainted 55% Al-Zn in most environments indicates a life on roofs of over 30 years before major maintenance.
  
  
• In 1999, field performance surveys of near-flat roofs (0.25:12, or 1°) and slightly sloped roofs (1:12, or 5°) in the United States showed that 55% Al-Zn roofs installed over 25 years previously were still providing very good to excellent protection on all exterior surfaces. The survey’s findings confirm that 55% Al-Zn is particularly suitable for use in aggressive acid rich (but not alkaline rich) environments.
  
  
• To achieve maximum durability, it is essential that suppliers’ recommendations concerning installation practice and contact with other construction materials are properly followed.
  
  
• 55% Al-Zn provides sustained cut edge protection whilst maintaining excellent long-term barrier protection. Corrosion resistance is two to four times better than that of hot-dip galvanised, 5% Al-Zn and aluminised coatings, which are not able to protect the steel over the long term.
  
  
• Excellent protection of the surface of the sheet is achieved because of the high aluminium content of the coating. The aluminium barrier is particularly stable because the surface aluminium-oxide layer is insoluble under most conditions, and thus provides superior long-term protection.
  
  
• 55% Al-Zn outlasts ordinary galvanised steel by two to four times. Atmospheric trials show that 55% Al-Zn sheets remain rust free after as much as 30 years in all but the most severe marine environments.
  
  
• The charts show exposure comparisons of 55% Al-Zn with galvanised steel in Northern Europe.