finishing.com -- The Home Page of the Finishing Industry
A website for Serious Education, promoting Aloha,
& the most FUN smiley you can have in metal finishing

HomeFAQsSuggested
Books
Help
Wanteds
Advertise
on this site
FORUM
(current
topics)
topic 5544

Alternate means of measuring conversion coatings


(2000)

Dear Sir or Ma'am, I am a quality engineer with a sheet metal manufacturing company. We have run across an issue with one of our customers regarding measuring chemical conversion coating on aluminum alloys. Their manufacturing specification is calling for the coating thickness to be between 0.00002-0.00005 inch. From the information that I have and the knowledge of the coating process which is limited to say the least I am questioning if this thickness is even possible. ASTM B449-93 [link by ed. to spec at TechStreet] is referring to coating mass in grams/meter square.

We have an instrument to measure paint and plating thickness (Fisher DualScope) but the ASTM spec it references to is the EDDY Current method and specifically states that chemical conversion coatings are not measurable under this standard. My questions are, is it possible to achieve a coating thickness desired by our customer spec. and can the thickness be measured without having to run test panels and weighing before and after.

Joseph M. Parker
- Smithfield, NC USA


(2000)

You are quite right; it is not possible to measure such thicknesses without very specialised equipment - electron microscope viewing prepared cross sections I think. The customer may be worried about fine tolerances (?). Chromate coating weights are measured by the strip and weigh method. If the panels are not hot air dried you can strip the coating using 30-40% nitric acid cold. Prepaint coatings are typically 0.3 - 0.8 g/sq metre (c. 30-80 mg/sq ft. R

Roger Bridger
- Croydon UK



This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Q or A to THIS thread START a NEW THREADView CURRENT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices


©1995-2017 finishing.com     -    Privacy Policy
How Google uses data when you visit this site.