Aluminium conversion coating is chrome-free

Iridite NCP is believed to be the first chrome-free conversion coating for aluminium to be approved and listed in the EU Qualified Products List for the MIL-DTL-5541F specification.

The European parliament has introduced strict new controls on the disposal of scrap cars and trucks, giving the original manufacturer a 'cradle to grave' responsibility.

MacDermid's range of electrophoretic lacquers now includes solid colours and low bake systems that crosslink around 120 deg C Iridite NCP is fast becoming the electronic and electrical industries' preferred choice for a RoHS compliant conversion coating for aluminium and now manufacturers can ensure they also meet the MIL-DTL-5541F spec.

MIL-DTL-5541 F is the latest update of the MIL-C-5541 specification and in line with current environmental guidelines, now allows the use of hexavalent chromium free conversion coatings under the Type II classification.

Only approved chemical materials detailed in the MIL-DTL-81706B part of the specification may be used to produce MIL compliant coatings.

Iridite NCP is the first and so far the only chrome free conversion coating for aluminium to be approved and listed in the Qualified Products List (QPL) for this specification.

In order to be approved to MIL-DTL-81706B, Iridite NCP passed the following performance criteria: corrosion resistance; paint adhesion; electrical resistance, before and after salt spray; and storage stability.

** Further reading.

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* Concentrate promises efficient, reliable cleaning - water-based liquid concentrate equips manufacturers with the means to remove metal working fluids, quench oils, drawing compounds and swarf, either between operations or as a final finish.

The MIL specification also calls for conversion coatings to be capable of being applied by immersion, spray and wipe.

Iridite NCP coatings passed the above tests when applied by all application methods.

Wipe, swab and brush application methods are most often used for repair of conversion coatings and as such they are quite often carried out in situ.

In order to make life easier for maintenance operations of this kind, a ready to use version of the Iridite NCP is now available called, Chemidise 800.

The Chemidise 800 is supplied as a ready to use liquid product.

It will produce Iridite NCP coating on small or single items or items which are too large to be treated in immersion tanks.

It can also be used to repair Iridite NCP coatings that have been physically damage or where rework/repair of the component has taken place.

The procedure is simple, starting with a cleaning step to remove any surface contamination, followed by treating with the Chemidise 800 solution by brush, swab, immersion or spray, whichever is most convenient.

Application time is short and after rinsing to remove any excess chemical, the coating is dried and painted as required.

The coating is hard and robust as soon as it is formed and does not require any aging or special curing time.

Painting can be carried out immediately although the coating will retain its paint receptivity far longer than chromates, allowing delays between coating and painting to be accommodated.

The Iridite NCP treated aluminium surface shows a high affinity for most high performance top coats including paints, lacquers, powder coating, adhesives and rubber bonding.

Where necessary, a simple test can confirm suitability.

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