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Re: alternatives to lead in autobody work



A short answer to your question is that  for pigments (i.e. in color
coats) used in auto refinishing, alternatives to lead are
well-developed, but not without trade-offs.  For primers, matching the
corrosion resistance of lead chromate could be more problematic.

Lead pigments are used for reds, oranges, and yellows. Some of the
well-established replacements with good color match include perylenes,
benzimidazolones, isoindolonones, and bismuth vanadate. The trade-offs
are:
* Metamerism.  The repainted part may not match the rest of the car
under all light sources. So the whole car needs to be repainted instead
of just one part.
* The reformulated paints have less hiding power, so they may need to
be applied thicker (e.g. 6 mil vs 2 mil)
* Higher cost

Pigment makers have been developing lead replacements since the 1977
lead standards  by EPA and by OSHA.   Lead-free pigments appear to be a
mature technology in that acceptable alternatives have been available
for several years, no new compounds have been introduced for several
years, and it's unlikely that prices will drop.

As Dave Salman mentioned, California recently passed a rule eliminating
chrome VI in auto refinish coatings.  Because the largest source of lead
is lead chromate, this rule has slashed lead emissions.  Within the
webpage he recommended, this information is presented in
http://www.arb.ca.gov/coatings/autorefin/atcm/901.pdf
For Massachusetts's salty roads, the corrosion protection offered by
lead chromate primers is more important than in California.

A flying google turned up some work Minnesota did on heavy metals in
auto refinishing in 1999.
http://www.pca.state.mn.us/waste/pubs/lm-arp.pdf  Although a little
out of date and in draft, this has a lot of information on tradeoffs and
issues that arise when reviewing specific coatings.



Mike.Heaney@erg.com  Senior Engineer, ERG Inc.  (919)468-7870    fax
(919)468-7801


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