To treat corrosion in old structures such as historic monuments, a comprehensive analysis has to be done to piece together the history of corrosion and the rate of corrosion taking place. Only then can restorers apply the necessary corrosion resistant coatings to the structure.
Chemical analysis can reveal the material composition of old structures, as well as the surface coatings previously applied on it. If there are any maintenance records, these documents will help a great deal in determining the chemical changes that occurred on the surface at various points in time.
Structural examination will reveal any cracks and holes in the monument, which are tell-tale signals of water entry on the base and other surface areas of the monument. Any color variations detected can also be due to surface corrosion, and must be repaired with the appropriate corrosion resistant coatings.
A non-destructive analysis involves gathering samples of patinas from various zones in and around the monument. Patina samples are gathered based on their exposures to rain water, sea water, and any particles or pollutants in the area. Patina samples can come from any side of the monument, such as the sea-facing side, or a busy highway on the other side, or in a sheltered surface or in a rain-exposed surface. Samples can also come from a porous region of the monument, or the basement, or wherever is determined that corrosion is actively taking place.
Science goes to work by measuring the polarization resistance of the surface with the help of a portable scanning equipment. An impulse current transmits valuable data of the surface, which yields the rate of corrosion in progress. The lower the corrosion rate, the better the performance of any corrosion resistant coatings applied to the monument’s surface.