Can anyone give me a definition of these.
I cannot find one which does not use the other!

I think "plating" is a subgroup of "coating" which is a very broad term.

In my world "plating" is where a conductive surface is coated with a metal.

I agree with ScottK as "plating" has a metallic influence. I think the difference is mainly the strength of attachment. Coatings utilize weaker bonds between the layers (cohesive) while platings utilize stronger, molecular bonds (adhesive).

Can anyone give me a definition of these.
I cannot find one which does not use the other!
FWIW:
I always thought of plating as pure "metal" bonded onto a metallic or non-metallic substrate. Plating can be with electricity, chemicals (electroless nickel for prime example), or mechanical action (usually tumbling with media mixture that gives a peening effect to the surface.)

I've thought of "coatings" as compounds, mixtures, and blends of materials (paint = pigments, binders, drying agents, etc.) which could be metallic or non metallic.

One of my primary sources for research on coatings and finishings for years has been a magazine for metal finishing - lots of experts on staff and good connections through the magazine to suppliers of plating and finishing materials. In recent years, they've opened a website http://www.metalfinishing.com/ which you may find helpful.

I agree with ScottK as "plating" has a metallic influence. I think the difference is mainly the strength of attachment. Coatings utilize weaker bonds between the layers (cohesive) while platings utilize stronger, molecular bonds (adhesive).

This is one of the differences that I thought.
The question arose in relation to CQI 11 and CQI 12 from AIAG (http://AIAG.ORG)
In this document SFDCN_COPIE07110507400.pdf (http://elsmar.com/Forums/attachment.php?attachmentid=7772) we can see that the techniques have a bearing

Is the definition the technology?

Hi Howard:

I belong to ASM (Materials Information Society), so I went there and looked up their definitions of the two terms. Here is what is in the ASM Metals Handbook Glossary of Metalurgical and Metalworking Terms;

coating
A relatively thin layer (<1 mm, or 0.04 in.) of material applied by surfacing for the purpose of corrosion prevention, resistance to high-temperature scaling, wear resistance, lubrication, or other purposes.

plating
Forming an adherent layer of metal on an object; often used as a shop term for electroplating. See also electrodeposition and electroless plating .

If you'd like to do a little more research for whatever the reason you are asking, I would recommend going to their Website, http://www.asminternation.org and snooping around. Hope this helps - or at least points you in the right direction...

-Steve