Definition - What does Laitance mean?
A laitance is a weakened layer of cement and fine particles on a concrete surface caused by a excessive level of undesired moisture or poor cement finishing.
Corrosionpedia explains Laitance
A laitance can be a contributing factor of corrosion. When metallic structures are adhered to or placed on a cement foundation with a laitance present, moisture can be trapped between the concrete and the metal surface, causing crevice corrosion or pitting.