Japanese steel repainting specifications use their own cleaning grades, such as 1種ケレン and 2種ケレン (1st- and 2nd-class keren), alongside ISO 8501-1 and SSPC/NACE grades. They are related but not identical, and definitions vary per project. Any tool or method has to be accepted per specification, never by assumed equivalence.
Surface preparation standards look universal, but each market has its own way of writing them into contracts. Japan is the clearest example. A tool that meets "Sa 2½" in Europe is not automatically accepted on a Japanese bridge repainting job, because the specification there may be written in Japanese grades.
The grades side by side
| Standard | What it is | How it is used in Japan |
|---|---|---|
| ISO 8501-1 Sa 2½ | "Very thorough blast-cleaning", a visual cleanliness grade | Cited in bridge repainting, plant and ship specifications, often alongside Japanese grades. |
| SSPC-SP 10 / NACE No. 2 | Near-white metal blast cleaning | Used in industrial and petrochemical contracts. Understood by most clients, but defined differently from ISO. |
| 1種ケレン / 2種ケレン (1st / 2nd-class keren) | Japanese cleaning classes for steel repainting | Bridge and steel repainting. Definitions vary per project and per owner. |
| NETIS (MLIT New Technology Information System) | Registration route for new technologies in public works | Not a cleanliness grade, but the credibility route that opens central and prefectural public works. |
What this means in practice
- Confirm acceptance per project. Ask the specifier which grade applies and whether a mechanical method is accepted for it. Never present one grade as automatically equivalent to another.
- Prove it locally. Test pieces and on-site demonstrations, measured against the grade in the specification, carry more weight than any international label.
- Follow the decision chain. In Japan the owner or consultant sets the specification, the general contractor or shipyard chooses the work package, the specialist contractor chooses the tool, and the distributor or rental partner supplies it. Each needs evidence in its own terms.
For the international standards in detail, see our complete guide to surface preparation standards.
Why it matters
Japan's infrastructure is ageing fast: by 2040 around three quarters of road bridges and two thirds of port facilities will be more than 50 years old. Getting the specification right is where prevention rather than cure starts. Speaking the local standard, instead of selling a translation of ours, is how we bring grit-free preparation to the people who maintain these assets (People), keep blast media out of rivers and ports (Planet), and earn a place in public works through evidence rather than claims (Power).
Working to a Japanese specification? MontiPower Japan can arrange test pieces and demonstrations against the grade in your contract.
→ Contact MontiPower Japan