Aluminium passivation

It is a chemical conversion layer on the aluminium surface. It increases corrosion resistance and stabilises electrical surface resistance. It is used where the part must remain conductive, or as a pretreatment before painting, bonding or spot welding.

Anodizing creates a thick oxide layer (clear 5 to 25 µm, hard 10 to 80 µm) that is hard and wear-resistant, electrically insulates the surface and changes the part’s dimensions. Passivation creates a thin conversion layer that preserves conductivity and dimensions but does not increase hardness. If you need hardness, wear resistance or colour, choose anodizing. If you need conductivity and corrosion protection or a base for paint, choose passivation.

Bonderite N2040 is a chrome-free, titanium-based passivation. It is used mainly to stabilise surface resistance and improve the long-term adhesion of bonded joints, and it meets the BMW 97022 process specification. SURTEC 650 is a TCP passivation. It is used for corrosion protection of conductive aluminium plates, as a pretreatment for spot welding and as a base for powder or wet painting. It meets QUALICOAT and GSB requirements and achieves 336 hours NSS to ISO 9227.

No. Bonderite N2040 is a chrome-free, titanium-based product. SURTEC 650 is classified as TCP, meaning it works with trivalent chromium and contains no hexavalent chromium. If your specification prohibits chromium in any form, choose Bonderite N2040. We do not offer chromating.

With SURTEC 650 it is 336 hours in neutral salt spray to ISO 9227. We choose the coating weight according to the purpose: 250 to 500 mg/m² for maximum corrosion protection, 50 to 200 mg/m² where low surface resistance is the priority.

Yes, that is exactly what passivation is often used for. SURTEC 650 serves as a base for both powder and wet painting, increasing adhesion and corrosion protection, and as a pretreatment for spot welding aluminium sheets. Bonderite N2040 improves the long-term adhesion of bonded joints.

The maximum part size is 3700 × 1700 × 800 mm; passivation runs on the same automatic line as anodic oxidation. Since June 2025 we have also had a new fully automatic robotic line for passivation and anodizing of aluminium for large dimensions and high-volume projects. We work on everything from single prototypes to series of thousands of pieces.

Parts must be free of residues of oils, emulsions and pastes and of swarf, especially from threaded blind holes; we recommend blowing out holes with compressed air. Products based on silicones, rapeseed oil, drying oils and waxes are not permitted. Parts must not be marked with paint or markers, taped, or contain components made of metals other than aluminium. Send the order and drawing documentation with the actual dimensions, defined contact points and visible surface together with the parts. State any requirement for masking holes, threads or surfaces directly in the order, not just on the drawing.