Our Finishing Processes - Black Passivation using Trivalent Chromates
The development of Trivalent Cr(III) for use in Black Passivates has become necessary in recent years as a result of the European legislation ELV (Directive 2000/53/EC) and further environmental legislations (RoHS and WEEE). The elimination of hazardous substances from coatings has resulted in the ban of Cr(VI) from corrosion protection layers and forced the industry to convert to Cr(III) based post treatments.
* Effective clear trivalent passivates emerged shortly after the ELV directive, however it took the electroplating industry longer to develop trivalent black passivates to match the appearance and performance of the old Cr(VI) black passivates.
* New products started emerging early in 2008 and by late fall RMF had completed a comprehensive review of new trivalent black passivates being offered in Europe, Japan and the US. The chemical manufacturers all have new product offerings and we wanted to perform side by side tests to determine which was best for us as an applicator and for you the customer. We tested rack and barrel plated trivalent blacks over zinc, zinc iron and zinc nickel.
| Plating Type | White (Zn) Corrosion |
Red (Fe) Corrosion |
Customer Compliance |
|---|---|---|---|
| Zn | 96+ | 300+ | Toyota TSH 6524G |
| ZnFe | 240 | 504 | Toyota TSH 6528G |
| ZnNi | 240 | 720+ | Volkswagen TL 244 |
In 2009, there will be a number of additional technological developments being rolled out at RMF. We will add a rack plating line using our new generation acid zinc nickel. This process offers an extremely consistent 10-15% nickel in the alloy through a very efficient acid electrolyte. Great applications for this technology are plating hardened materials and iron castings.
Another area of focus at RMF is our new offering of sealers and top coats to meet the future needs of the automotive market. Stay tuned for more details on sealers, topcoats and zinc flake products:
- Come in silver and black colors
- Can be applied direct to the parts or over zinc or zinc alloys
- Are free of chromium, nickel, mercury and lead
- Are non-electrically applied meaning no risk of hydrogen embrittlement
- Exceed 1,000 hours salt spray (DIN 50021 SS, ASTM B633)
- Have minimal coating thickness
- Can withstand high temperatures (180C) without reducing corrosion protection or optical appearance.
- Come with a number of friction coefficient options
- Are chemical resistant - fuel/brake fluid, etc.
Back to Finishing Processes...
