Hexavalent-chrome-free
Conversion Coatings
As industry moves away from hexavalent chromium under RoHS, ELV, and WEEE, we offer the hexavalent-chrome-free trivalent alternatives: Iridite NCP and SurTec 650, both trivalent conversion coatings for aluminium. For stainless steel, see our citric passivation service.
- Substrates
- Aluminium and aluminium alloys
- Standards
- MIL-DTL-5541
- Turnaround
- 3–5 working days
MIL-DTL-5541 Class 1A gives maximum corrosion protection, painted or unpainted. Class 3 is used where low electrical resistance matters, such as bonding and earthing points.
Iridite NCP: trivalent chromate conversion (aluminium)
A protective trivalent (hexavalent-chrome-free) conversion coating for aluminium that improves corrosion resistance while keeping electrical conductivity and giving a good base for paint or powder coat. For stainless steel passivation, see Passivation.
| Materials | Aluminium and aluminium alloys |
|---|---|
| Finish | Clear / iridescent · minimal added thickness |
| Key properties | Corrosion resistance with retained electrical conductivity; good paint/bond base |
| Standards | MIL-DTL-5541 Type II, Class 1A & Class 3 |
| Compliance | RoHS and REACH compliant |
| Turnaround | Typically 3–5 working days |
| Typical uses | Aerospace, defence, electrical enclosures, precision engineering |
SurTec 650 / 650V: trivalent conversion coating (aluminium)
A high-performance trivalent (hexavalent-chrome-free) conversion coating that sharply increases the corrosion resistance of aluminium components, while keeping electrical conductivity. Widely specified in aerospace, defence, and electronics.
| Materials | Aluminium and aluminium alloys |
|---|---|
| Finish | Clear · minimal added thickness |
| Standards | MIL-DTL-5541 Type II, Class 1A & Class 3 |
| Compliance | RoHS, REACH, ELV, and WEEE compliant |
| Turnaround | Typically 3–5 working days · 24-hour service on request |
| Typical uses | Aluminium enclosures, brackets, and machined components |
Maximum part size
| Finish | Max weight | Max size (L × D × Br) |
|---|---|---|
| SurTec 650 | 35 kg | 800 × 300 × 800 mm |
| SurTec 650V | 35 kg | 800 × 300 × 800 mm |
| Iridite NCP | 35 kg | 800 × 300 × 800 mm |
Frequently asked questions
- ISO 9001 certified
- Made in Britain member
- IMF member (Institute of Metal Finishing)
- Free Certificate of Conformity
- Fast turnaround: 3–7 days, 24-hour service on request
- 25+ years’ combined experience