10W Engraving on Ammo Cans

I have used my Longer 10W to burn literally hundreds of powder coated Ammo Cans. During my most recent burn the displayed metal has begun to turn a goldish color. I have done a material testing and still can not get it to return to the silver it was. I have tried multiple combinations of speed and strength, changed the lens, tried various cleaners and multiple cans. Can anyone provide any input as to what the issue is?

Materials from the same source can vary in both quality and composition. The same item from different vendors is even worse.

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Thank you.
I have purchased all of the Cans from Harbor Freight. I know that there are some variations in the powder coating color, but this has never been as issue before. Do you believe some of the issue may be the supplier that HF uses may have changed?

The consistency of ammo cans is probably quite poor - thicker/thinner paint would be an issue, as would the paint composition itself. Discoloration of the base metal can also be a heat affected zone from local heating caused by the laser.

This is a very strong possibility based on my experience with their products. They think “slightly different” will not matter. :nerd_face: