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topic 10311

Adhesive bond failure to Zinc Plated/Passivated Parts

An ongoing discussion from 2001 through 2016 . . .


Q. Does anybody have any experience of adhesive bonding zinc plated and color passivated components to GRP (Glass Reinforced plastic). We supply a component that is assembled into a seat, during torquing we are seeing occasional failures of the adhesive to the zinc plated surface. The adhesive is a two part methacrylate, and the failure appears to be at the interface between the passivate and the zinc surface.

Prior to bonding the parts pass a tape adhesion test of the passivate film. The components are degreased by wiping with IPA prior to bonding.

Any thoughts?


Richard Guise
- Lowestoft, U.K.


A. We've seen instances where wiping the conversion film with IPA will remove it. If this is the case, try drying the zinc plated parts with a higher temperature for a longer time after the conversion coating is applied.

Also, your company may want to specify a rougher surface prior to zinc plate. A rougher surface will enhance a mechanical bond to the GRP.

Richard Painter
- Cleveland, Ohio

October 7, 2011

A. Hi,
We also experienced a similar problem in rubber-to-metal (zinc plated + Cr3 coated) bonded parts. If the failure appears to be the interface between the Plating & the passivate, the cause will be the presence of charged particles over the plating surface, it requires neutralization. Normally nitric acid can be used as a neutralizing agent before passivation.
If the failure occurs to be the interface between passivate and the adhesive coating, please verify the alternate degreasing agent before adhesive coating.

- Madurai, Tamilnadu, India

January 2, 2016

Q. My question is why does chrome-free white zinc coating not react with adhesive made by mixing resins and hardeners in winter season ... while it works well in summers, and with yellow zinc coating as well?

Prateek Sarin
- New Delhi, Delhi, INDIA

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