George: Type III chromate conversion coatings really don't offer much environmental protection. However they do offer some protection as opposed to straight zinc. Are the fingerprints reacting and etching into the zinc plating or do they just show up on the surface of the coating? I would expect a properly applied coating to resist some handling. Obviously a Salt Fog or Salt Spray test would help to give you some quantitative indication of the quality of the coating, but that takes time and equipment. You can also do a weight loss test by weighing the part, stripping the coating and re-weighing. I've used this method on aluminum with class 1A coatings with success. However the accuracy of this for very thin coatings is not the greatest and may be difficult for stripping the coating from a zinc substrate. A spot test can also be done. This is strictly a qualitative test but has a very high sensitivity to the presence of Chromate. It will not tell you the quality of the coating but it will definitely tell you if any Chromate is present. Make a solution of 0.1% B.W. diphenylycarbazide to reagent grade methanol. Place a drop on the suspect part. If there is Chromate present it will turn a brilliant violet color. Good Luck Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: Wenger, George M. [mailto:[log in to unmask]] Sent: Friday, May 02, 2003 12:26 PM To: [log in to unmask] Subject: [TN] Type 3 Chromate Conversion Coating If a cold rolled commercial quality steel (per ASTM A366) assembly that is zinc plated (0.0002" min per ASTM B633 Type 3) and supposed to be colorless chromate conversion coated begins to show finger prints and surface tarnish in a relatively benign environment, should you suspect that the chromate conversion coating is missing or improperly applied? And secondly, is there an analytical method to determine the presence and quality of the coating or would one have to resort to Salt Fog testing Regards, George George M. Wenger (908)-546-4531 Reliability Engineer RF Power Amplifier Group Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 [log in to unmask] ---------------------------------------------------------------------------- ----------------------- This message is for the designated recipient only and may contain privileged, proprietary, or otherwise private information. If you have received it in error, please notify the sender immediately and delete the original. Any unauthorized use of this email is prohibited. ---------------------------------------------------------------------------- ----------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------