Greetings to all:

With the recent ELV regulations upon us we have all had plenty of exposure to the trivalent chemistries of today. We thought this would be a good time to introduce a recent case study that was performed by Toyota…

Toyota Study - Trivalent Parts Turn Hexavalent Over Time. Why?

Study done by:

Toyota Motor Corporation
Mr. Morimichi Miura
Assistant Manager
Quality Audit Department
Quality Division

They have discovered that in some cases trivalent zinc parts are turning back to hexavalent over time. Clearly with the ELV regulations and potential costs to the OEM if cars are found to have ANY hex chrome at the end of their vehicle life, this is a major concern.

Toyota (Mr. Miura, Quality Audit Department – Japan) conducted a study on parts from several of their top Tier suppliers coming from over 200 zinc plating lines at over 100 plating operations. The report is very technical but the gist of it is that Toyota feels that high cobalt in the presence of any chelator can cause parts to turn from trivalent back to hexavalent over time.

Chelators - acid zinc (ammonia), cyanide zinc and organic trivalents (most trivalent passivates on the market are organic acid based – TR 175 is INORGANIC)

Cobalt - All trivalent passivates are high in Cobalt.

Toyota tested the three types of zinc plating electrolytes that are most common in Japan; zincate (alkaline zinc), cyanide zinc & chloride zinc. Tests were run on all three types of zinc with both organic & inorganic trivalent passivates. The only combination that had no result of hexavalent chrome over time was zincate and inorganic trivalent. (Alkaline Zinc & TR 175 is an example of this combination). The best counter measure is to use zincate & inorganic trivalent. (Alkaline Zinc & TR 175 qualifies as counter measure).

That said, Coventya is the only manufacturer in the states that has the TR-175 Trivalent clear chemistry available. We have included some of the product literature on our featured products page.

For additional info or to view the whole case study please contact us directly.

Cordially,

Ryan Bustard
Mibus Inc.
630-258-6485
rbustard@mibusinc.com