Anti-corrosion technology for automotives with no heavy metals

Materials World magazine
2 Oct 2007

International Ford Motor Company has developed an anti-corrosion technology that does not use heavy metals. The company claims this reduces water use in automotive paint shops by half, decreases the production of waste sludge by 90% and makes the entire pre-treatment process more efficient.

The technique makes use of a zirconium oxide vehicle bath rather than the conventional heavy metal zinc phosphate bath. The traditional process comprises 13 steps. The phosphate stage involves a three-cation heavy metal material (zinc, nickel and manganese) conversion coating. The bath is 140,000 gallons and is kept at a constant temperature of 120ºF (48.8ºC).

Tim Weingartz Manager of Paint Materials and Strategy, based in Dearborn, USA, explains, ‘The chemical reaction creates a sludge in the bath that needs to be filtered out and then hauled away. The vehicle bodies then pass through two stages of city water rinse [and] four stages of de-ionised water to ensure that [they] have been completely rinsed of all residual cleaner and phosphate chemicals before they enter the electrocoat dip system.’

The zirconium oxide-based system cuts this entire process down to eight steps, and is said to be comparable to zinc phosphate in its corrosion resistance properties.

Weingartz says, ‘The current system consists of multilayers of protection. The main components are two-sided zinc coated steel, dip phosphate and lead-free electrocoat. Zirconium oxide in this application is not a crystalline structure like zinc phosphate, but an amorphous and thinner coating on the steel surface.

‘The new process is more environmentally friendly because it does not use bio-accumulating heavy metals, it does not generate sludge, does not need to be heated [saving energy] and reduces the amount of water used.’ The technology can be run at ambient temperatures. Field tests will continue up to early 2008, when Ford will determine its rollout plans to paint shops in North America.

‘Even though zinc phosphates are robust and provide excellent corrosion protection, there is potential that heavy metals will be regulated in the future,’ adds Weingartz.


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