Rust on Coating Surface

[pgr380]

Just did a visual inspection of clarifier mechanism coatings at domestic wastewater plant. Coating, Tnemec 141, 10-12 mils, has been in service for 12 months. Discovered surface rust in several locations on structural steel angles. No visual indication of coating failure as the coating underneath seems to be adhered and intact (rust can be wiped away with a wet cloth). Could the rust be caused by pinholes (no holiday testing was required after application)?

 

[bimr]

If you can wipe it off with a rag, are you sure it is rust? How about posting a picture?