A contractor washed cement plaster off an enamel painted, metal roof with HCL.?

Roof has a 45 deg pitch. he then washed down the roof. from the next day we then had three days of rain. The owner says the roof must be replaced. She says that the more you add water to HCL, the more corrosive it becomes. I understand that a roof isn't a container and that adding water must (1) dilute it and (2) remove it. can someone please offer some solid scientific answer that may help here. this poor guy needs the factsA contractor washed cement plaster off an enamel painted, metal roof with HCL.?
HCl is soluble in water. Adding water to a HCl solution dilutes the acid. Add enough water and the HCl solution approaches the acidity of rain water. The HCl has been completely washed away by 3 days of rain. There certainly won't be any HCl solution left on the roof. The HCl was probably washed away by the contractor when he rinsed off the roof after cleaning it.





The owner is confused about HCl. The gas, HCl, ionizes in water and is corrosive. Exposing the roof to concentrated HCl solution is more corrosive than exposing a dry rood to HCl gas. However, the more water you add to a HCl solution, the weaker (and less corrosive) it becomes.