Standard · Systems, environments and degradation
ASTM D610
Rating the degree of rusting on painted steel.
ASTM D610 and the SSPC-VIS 2 pictures rate rust on painted steel by two things. The first is how much of the area shows visible rust, on a scale from 10 (least) to 0 (most). The second is how the rust is spread: spot, general, pinpoint or hybrid. A rating gives both.
Compared with ISO 4628-3
ISO 4628-3 rates red rust from Ri 0 to Ri 5 against pictures. Its calibration pictures stand for about 0.05 % rusted area at Ri 1, 0.5 % at Ri 2, 1 % at Ri 3, 8 % at Ri 4 and 35 % at Ri 5. The 2024 edition corrected Ri 5, which older texts give as 40–50 %.
The two scales run in opposite directions. In ASTM D610 a high number is good; in ISO 4628-3 a high number is bad. Check which scale a report uses before comparing two surveys.
What the rating decides
Owners use these ratings to choose between spot repair, overcoating and full removal. ISO 12944-1 gives an example: first major maintenance is normally due when about 10 % of the coating has reached Ri 3.
5 practice items in the members area mention ASTM D610 (CIP 1: 2 · CIP 2: 3).
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Also published openly: Henkel / CCAI corrosion evaluation legend: ASTM D610 and D714 scales · Coatings Radar: ASTM D610 and ISO 4628-3 rust scales.
This page describes the subject of ASTM D610 in our own words; it does not reproduce the standard. For the full text, buy the current edition from ASTM International. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.