Search our quarter-million Q&As

Home of the finishing HOTLINE since 1989

-----

Max. temperature for chromated surfaces?

Our product is made of die cast aluminum and must be chromated and epoxy coated. According to our supplier it will raise problems because the chromating temp. is 80° C max allowed whereas the epoxy coating temp starts at 120 °C. This higher temp. will have a negative influence on the chromating.

Gerrit Buist
Supervisor QA/QC - Scherpenzeel, Gelderland, The Netherlands
2004

---

Cure the chromate at room temperature. Put it on light if it is to be painted. The paint curing temperature will not degrade the chromate that is covered with paint. Any uncovered areas will be degraded (moisture driven off and flaking).

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2004

Chromate degrades rapidly at temperatures exceeding 140 °F. Severe dehydration is suspected. A heavy chromate film may lead to large flaking of the exposed treated surface. Although the painted surface will help protect the chromate treatment below, your interface surface of the dehydrated chromate to another assembly may cause corrosion issues in that area.

Toby Tenorio
Metal and plastic finishing. - Clearwater, Florida, USA
2004

---

Although the responses from Mssrs. Probert and Tenorio are largely accurate, they are also from an earlier time when hexavalent chromating was the rule. These days proprietary trivalent chromates have largely supplanted hexavalent chromating due to RoHS and other international standards. These proprietary trivalent chromates differ greatly one from the other: thin film, thick film, topcoat, no topcoat, etc. It becomes difficult to answer the question of temperature limitation generically and some of the coatings claim to be quite immune to temperature issues, and a suitable base for powder coating despite its high curing temperatures.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
November 4, 2008

Sorry! Finishing.com is temporarily Read-Only.
Please maintain your bookmarks! Although Ted Mooney is retiring, finishing.com is not!
It will have a new owner/curator very shortly!