V&A developed the VANDA® Metal Condition Index Rating System as a means to consistently identify the condition of metal.
Metal surfaces are rated according to the following table, which summarizes this metal condition rating system. The condition of metal corrosion can vary from Level 1 to Level 4 based upon visual observations and ultrasonic thickness data collected in the field, with Level 1 indicating the best case and Level 4 indicating severe damage.
VANDA Metal Corrosion Index Rating System
The submerged, immersed, and non-submerged ferric surfaces do not show indications of corrosion damage (click thumbnail for larger picture).
Localized corrosion damage of the ferric surfaces in the form of pits. Depth of pits can range from small to large. Measuring these pits will determine the extent of corrosion loss at the localized area (click thumbnail for larger picture).
Top layers of the ferric surface have corroded and exfoliated or flaked off (also referred to as scaling). The extent of corrosion can be determined by removing corroded surfaces, and performing ultrasonic thickness testing. A direct measurement cannot be used as the exfoliated and corroded metal has expanded to many times its original thickness during the corrosion process (click thumbnail for larger picture).
Loss of Metal Material
The extent of exfoliation has reached a degree wherein the remaining thickness of metal is not sufficient to maintain the structural integrity of the structure (click thumbnail for larger picture).