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Corrosion in rivet head

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Dear Sirs,

My Company manufactures parts for Automotive Air Conditioning Systems (Compressor Clutches). I need to solve an issue raised by final customer regarding steel rivets protection. Rivets are protected against corrosion (Zinc+Iron plated, passivated in Black) and, as an unused part, they can pass the Salt spray test 96h (even 200h) easily. What happens is, after rivets have been riveted, some spots of the Rivet "head" loose the protection. How can we fight this? Somebody proposed using "Electrolitic zinc plate, trivalent chromate, leached and sealed". Can you explain what is this?

Thanks in advance.

Best regards,

José Teixeira Pinto
- Lisboa, Portugal

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Mr Pinto,

The following may help.

1) The Zinc Iron Plated Rivets should be coated with a water Soluble lacquer after being black passivated.

2) After the rivets have dried fully these must be left in storage to cure for 24 to 30 hours and used only after curing.

3) If the the riveting operation imparts a hit on the head of the rivet, chances of damage to the lacquer and Black passivate coat are entirely possible.

Try a dirrerent riveting technique which essentially is a firm squeeze rather than a strike. That is a press operation..

4) try using a NON SILVER based passivate followed by lacquer.The color is not as shiny , but cosmetics are not an issue, whereas Corossion protection and abuility to withstand riveting are the issue.

Non Silver passivate films are a bit tougher after being fully cured. And lacquerd.

Hope this helps.

Regards,

Asif Nurie Atlanta Global New Delhi, India