Product category:
Materials and components
News Release from: MacDermid | Subject: Iridite NCP
Edited by the Engineeringtalk Editorial
Team on 24 January 2006
Coating aids chrome elimination process
If done correctly, eliminating chrome from the workplace should benefit the environment and worker safety, and not increase the overall cost of a company's products.
MacDermid is recommending its Iridite non chrome passivate (NCP) product to help eliminate chrome from the workplace to benefit the environment and worker safety, and not increase overall costs Developed in 2002, Iridite NCP is totally inorganic using the same application methods and parameters as traditional yellow chromates
This article was originally published on Engineeringtalk on 14 Nov 2006 at 8.00am (UK)
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The bath and resulting coating does not contain any banned components found within the RoHS, WEEE and ELV directives.
The chemistry is reactive, unlike the polymer based chrome free paint pre-treatments, so it can be completely rinsed after application thus extending bath life and performance.
As with the yellow chromate, Iridite NCP has bare corrosion resistance without painting and paint adhesion characteristics.
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As the application procedure is practically identical to the yellow hexavalent chromate, it has been tested head to head using a standard conversion coating process.
Using the ASTM B117 salt spray test on conversion coated panels, Iridite NCP gave in excess of 1000hr on most 1000, 3000, 5000 and 6000 series alloys, which was better than that obtained from the traditional yellow chromate.
The main cause of poor salt spray resistance in aluminium alloys is copper content, and copper levels above 2% greatly reduce salt spray life.
Chromate conversion coatings still outperform Iridite NCP when used on these alloys although even chromate has limited salt spray life on high copper alloys.
Due to their low inherent corrosion resistance, high copper alloys are rarely used in applications requiring high corrosion resistance without painting or cladding, in which case Iridite NCP is still suitable.
When painted, all Iridite NCP panels, regardless of alloy, passed 1128 hours salt spray with neither creep from scribe nor loss of adhesion with a cross hatch and tape pull test.
Electrical chassis and enclosures are often made from chromated aluminium to allow electrical grounding while still providing corrosion resistance.
Iridite NCP will meet the MIL-C-81706 electrical resistivity test before and after salt spray ensuring continued performance during service.
To accept paint properly, the coating must be intrinsically hydrophilic so the surface wets out to allow the paint to flow.
Besides being a drop-in replacement for chromates, Iridite NCP can be used by the manufacturer and subcontractor.
A traditional yellow chromate coating forms as a soft gel on the metal surface, which is susceptible to damage and takes 24hr to cure to a reasonably hard film.
If left in the tank, the chromate will continue to build up, becoming lose, powdery and non adherent.
The Iridite NCP coating is self limiting, producing a hard amorphous coating as formed and does not require any curing time. Request a free brochure from MacDermid ...
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