- IP66 (IEC 60529) means total dust-tightness and resistance to powerful water jets. It is not a pressure-immersion test — condensation from thermal cycling can still accumulate inside.
- IK10 (IEC 62262) means the enclosure withstands 20 joules of mechanical impact. It is a single drop-impact test, not a cumulative wear test.
- C5-M (ISO 12944-2) is the highest corrosion environment class — marine/industrial with high humidity and salt. A luminaire with C5-M paint coating has been tested under extreme environmental stress, but protection is only as good as the application quality of the surface treatment.
- None of the three ratings is a test of long-term performance under field conditions. They are standardised point-in-time tests under defined laboratory conditions.
Dust: no ingress
Water: powerful jet (12.5 L/min, ≥ 30 s)
Pressure immersion: not tested
Impact energy: 20 J
Method: 5 kg hammer from 400 mm
Test: one point, one impact
Environment: extreme marine/industrial
Corrosion test: ISO 9227 (salt spray)
Expected coating life: H = >15 years
IP Rating — Ingress Protection for Dust and Water
IP stands for Ingress Protection. The system is defined in IEC 60529 and applies to all electrical equipment. An IP code should be read as two digits:
| Digit | Protection against | Value 6 means |
|---|---|---|
| First digit | Solid objects and dust | Total dust-tightness: no dust ingress over an 8-hour test period under negative pressure |
| Second digit | Water | Protection against powerful water jets: at least 12.5 litres/minute from any angle for at least 3 minutes |
IP66 is the most common rating for street luminaires. Note that it is a point-in-time test: the luminaire is tested new, with complete gaskets, under laboratory conditions.
What IP66 Does Not Test
- Thermal pumping: When a luminaire heats up, the air inside expands and is pushed out. As it cools, a partial vacuum forms and moisture is drawn in. This occurs even in a correctly IP66-rated luminaire — the IP test is conducted at static temperature.
- Gasket ageing: Rubber gaskets harden and crack over time. The IP66 marking says nothing about how long the seal holds under UV radiation and temperature cycling in the field.
- Pressure immersion: This is tested by IP67 (submersion 1 m, 30 min) and IP68 (longer duration/depth, defined by the manufacturer). For harbour environments and flood-prone locations, a higher class should be considered.
See Moisture, Condensation and Failure Modes for the full discussion of why IP class alone does not rule out moisture damage.
IK Rating — Mechanical Impact Resistance
The IK code (IEC 62262, harmonised as EN 50102 in Europe) grades mechanical impact resistance from IK00 (no protection) to IK10 (highest class). For street luminaires, IK10 is the relevant minimum requirement in exposed environments.
| Class | Impact energy (J) | Test method |
|---|---|---|
| IK08 | 5 | 1.7 kg hammer, 300 mm drop |
| IK09 | 10 | 5 kg hammer, 200 mm drop |
| IK10 | 20 | 5 kg hammer, 400 mm drop |
20 joules corresponds approximately to the energy of a 5-kg stone falling freely from 40 cm. For a street luminaire with a glazed cover, IK10 is relevant — but it is a single impact on a specified point, not a simulation of a year's worth of potential field stresses.
What IK10 Does Not Address
IK10 tests one impact at a given point. It is not a wear test of, for example, hinges, locks, plastic clips, or the cumulative effect of vibration in high-mast installations. It is not a vandalism simulation either; a chisel or hammer concentrates energy on a smaller area than the fall test and can locally exceed the IK10 threshold.
C5-M — The Corrosion Environment, Not the Maintenance Coat
ISO 12944 Protective paint systems divides corrosion environments into classes C1–C5 plus CX and CX-offshore. C5-M (“M” for marine) is the second-highest class:
| Class | Environment | Typical example |
|---|---|---|
| C1 | Very low | Heated indoor space |
| C2 | Low | Rural area with low humidity |
| C3 | Medium | Urban environment, coastal industry |
| C4 | High | Industrial with high humidity, chemical environment |
| C5-M | Very high (marine) | Coastal areas, salt spray, seaside care homes |
| CX | Extreme | Offshore platforms, industrial extreme environments |
A luminaire bearing a C5-M designation for its coating has been tested via ISO 9227 (salt spray, 1000+ hours) and meets ISO 12944-6 for the expected durability category H (>15 years). It is a classification of the surface protection system (primer, intermediate coat, topcoat, dry-film thickness) — not of the housing material itself.
C5-M, SMC, and Aluminium
Here there is an important distinction:
- Aluminium with C5-M coating: Aluminium oxide (spontaneous oxidation) provides some base protection, but heavy salt deposition on damaged paint areas accelerates corrosion. The coating system is critical.
- SMC thermoset: Glass-fibre reinforced thermoset does not corrode and requires no surface protection system for corrosion resistance. Salt spray testing is not relevant to the housing itself. The surface treatment (pigment/lacquer) is a UV and aesthetic question, not a corrosion question.
See SMC, Aluminium and Cast Iron for a deeper comparison of housing material corrosion resistance.
What Municipalities Should Ask About
- IP class + gasket properties: Require the manufacturer to disclose the gasket type (material, Shore hardness) and recommended replacement interval. IP66 at delivery is not IP66 after 10 years without maintenance.
- IK class on the exposed surface: Which component was tested? The glass cover, plastic lens, or housing? The luminaire's actual impact point in the field may differ from the test point.
- C5-M: require an ISO 12944 test certificate. Request salt spray test results per ISO 9227 and a test protocol from an accredited institute. Not just “C5-M” on the data sheet.
- Housing material vs. surface protection: For coastal installations, the choice of housing material (SMC vs. aluminium) is at least as important as the paint system.
- Combination of ratings: IP66 + IK10 + C5-M means the luminaire passed three separate laboratory tests — none of which simulates 20 years of combined moisture ingress, mechanical stress, and salt exposure under combined field conditions.
VALDUR — Technical Note
VALDUR has an IP66-rated SMC housing. The SMC does not require a paint system for corrosion protection — corrosion resistance is inherent in the material. IK10 is tested on the housing surface panel. For coastal installations, IP66 is sufficient without C5-M coating (since SMC does not corrode). More on the material thinking behind the housing: SMC, Aluminium and Cast Iron.
Related Articles
SMC, Aluminium and Cast Iron
Why SMC requires no coating for corrosion protection
Moisture, Condensation and Failure Modes
Why IP66 does not rule out moisture damage and how thermal pumping occurs
EN 13201 — Road Lighting Classes
ME classes, uniformity, and what to specify in tender documents
Why Luminaire Housings Corrode
Corrosion mechanisms in street luminaires in coastal environments
Sources
- IEC. (2013). IEC 60529:2013: Degrees of protection provided by enclosures (IP Code). (IP ratings, test methods and requirements.)
- IEC / CENELEC. (2021). IEC 62262:2021 / EN 50102:2021: Degrees of protection provided by enclosures for electrical equipment against external mechanical impacts (IK Code).
- ISO. (2018). ISO 12944-2:2018: Paints and varnishes — Corrosivity categories. (C1–C5-M classes and environment descriptions.)
- ISO. (2017). ISO 9227:2017: Corrosion tests in artificial atmospheres — Salt spray tests. (Test method for C5-M verification.)
- ISO. (2018). ISO 12944-6:2018: Laboratory performance test methods. (Test protocol for protective paint systems per corrosion class.)
- van Bommel, W. (2015). Road Lighting: Fundamentals, Technology and Application. Springer. (Environmental requirements and material considerations for road luminaires.)