Non-Lead Electrocoat

Ask an Expert From: Products Finishing, from Finishing Help, LLC

Posted on: 6/1/2003

Question: We have received complaints from our customers about “scuffing and scratching” on bulk packed parts.

Question:

We have received complaints from our customers about “scuffing and scratching” on bulk packed parts. This seems to have increased since our suppliers have switched to non-lead Electrocoat. Is this the cause of these defects? Why was lead removed? RT

Answer:

Many of the original automotive body and custom coaters used lead-containing electrocoat materials. The lead containing pigment was left in the products for two basic reasons:

 

  1. Protect equipment that was originally designed for anodic electrocoat. When these tanks were converted from anodic to cathodic, corrosion of the non-stainless steel equipment was a concern. Since the anodic material was alkaline, some pumps and piping were carbon steel and the lead-containing pigments coated these components and prevented them from corroding.
  2. Corrosion resistance of the coated parts were believed to be better with the lead-containing pigment. This was true for parts that had marginal or no pretreatment such as door, hood and trunks that were double-walled. For parts that were adequately pretreated, the “lead- and chrome-free” materials provided equal corrosion resistance to the lead-containing materials. As cathodic electrocoat materials were improved and wastewater restrictions were increased, the lead was removed without reducing the corrosion resistance of the coated parts.

 

When I was running a custom coating operation, we had one of the first “lead and chrome-free” tanks and bulk packed quite a few parts without any customer complaints. As more parts were converted to Electrocoat from liquid and powder, we found that aesthetic requirements were increased, and bulk packing was not acceptable (depending on the cost difference).

Having worked with a custom coater in Michigan who went through the conversion from lead-containing to lead-free electrocoat, I asked them if they noticed any increase in “scuffing and scratching” defects. They responded with several points:

 

  1. No change in “scuffing and scratching” defects when the switch was made to lead-free material.
  2. No change in pencil hardness when the switch was made to lead-free material at the same baking schedule (cure time/temperature).
  3. If cure schedules were decreased (to reduce energy, gloss loss, or coating shrinkage), some additional “scuffing and scratching” defects might be seen.
  4. End users have continued to “raise the bar” to a Class A requirement, which has caused changes from bulk pack to more nest and layer packing.
  5. Packaging changes to smaller containers are also related to ergonomics and space at the assembly line.

 

Therefore, I do not believe the elimination of lead from the electrocoat raw materials should have caused your increase in packaging requirements. Please review the other options listed above to see if these might be the reason(s).

 


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