plating, anodizing, & finishing Q&As since 1989
Flat black finish throughout a small tube.
Hi, We need to achieve a consistent flat black finish throughout a small tube. The material consists of honey combed aluminum The cells are 1/4" dia. & 1-1/4" deep. We are having a hard time getting flat black paint down to the center section of the honeycomb. Any ideas on how we might get better results?
- Fremont CA.
Jon - A possible way to blacken the inside of the tubes you describe is to use a room temperature black oxide. That way, there will be a uniform coating on the part, and no drips, etc to deal with.Dan Brewer
chemical process supplier - Gurnee, Illinois
If the paint is something you need to stick with, there are some avenues you can pursue to improve coverage into the cavity areas. Angle of spray, atomizing air pressure, viscosity of the paint and paint pressure all will affect the ability to cover inside the cavity. If the finish will abide it, an airless or air-assisted airless will give you better penetration into the cavity than conventional air spray. This is true because there is no (or less with the air-assist) atomizing air pressure encouraging the paint droplets to blow back out of the cavity. If airless spray is not feasible, HVLP tends to offer better penetration also. This is particularly true on systems in which the paint is pressure-fed to the gun. The "siphon fed" HVLP will not offer as good coverage. Once you've established the appropriate method of application, you're better off using a robot or other automated application. This will ensure that as you fine-tune the pattern for coverage, human variation will not be a factor.Michel Moninger
- Sarasota, Florida
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