Corrosion products occupy more volume and can crack surrounding concrete or masonry.
Visible fingerprint
rust staining, longitudinal cracks and spalling.
What controls the reaction
Duration, temperature, moisture source, drying potential, material thickness and previous finishes all change the outcome.
What the surface cannot prove
A material response can reveal exposure without identifying the original source. Follow interfaces and adjacent layers before selecting a repair.
Verification
After correcting the source, record whether moisture, shape, odor or finish condition stabilizes over an appropriate period.
Material laboratory ruleA surface can show exposure, transport or damage. Do not assume the visibly affected material is the original source.
