Letter 15638

Thickness measurement of phosphate coatings  

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I am doing a project on the phosphate coatings as my final year project in B.Sc Engineering at University of Moratuwa, Sri Lanka. At the moment we do not have a proper method to measure the thickness of the phosphate coatings, which were developed during the project. Please be kind enough to give any information on the thickness measurement of the phosphate coatings. Any documents of researches carried out under the above topic are very much appreciated.

Bhatiya Dewagiri
- Colombo, Sri Lanka

Hi Bhatiya,

Do you mean the acutal thickness of the coating, or the amount of phosphate coating that has been deposited?

The actual thickness is difficult to measure because there is no clearly defined boundary between the coating and the base metal. Remember that the top portion of the metal surface has been converted into the phosphate coating.

The amount of coating can be determined gravimetrically by immersing a phosphated panel into a soultion of chromic acid.

A good discussion can be found in Werner Rausch's book, "Phosphating of Metals" [link is to info about the book at Amazon]

George Gorecki
- Naperville, Illinois

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