Color variation between thick and thin parts

Dave,

  Differences in color can come from many sources: oxide layer thickness, oxide layer porosity, differences in temperature during the process(es), differences in base material, etc

Are you sure that your 1mm samples are from the exact same stock as the 0.25mm parts?  Even slight differences in alloy can make a noticeable difference to the human eye.

The thicker parts may carry current more easily, allowing them to build up a potentially thicker oxide layer.  Have you checked the actual coating thickness on both parts?  In general, the thicker your coating, the more uniform your color will be.

Hi Dave

Great answers Dustin, just one more comment.

Even the same alloy with the same thickness can give color difference. What we need to talk about is the microstructure and not the alloy. Often the dispute is about alloy composition and the analysis shows that the alloy is the same and also in the specification range.

So why not the same color? the reason for this is the microstructure which can be totally different for the exact same alloy.

What you should do in this particular case is to be sure that both parts, thick and thin, have the same microstructure. Depending on the metallurgical history of the 0.25 mm part, you will know how to get the same microstructure for the 1 mm part.

I have to say that the easy way out is to have the same thickness of the standard color chips, and actually always have the actual part as a reference.

Sunny regards

Anne

www.anodizingworld.com