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Anodizing a cast A380 aluminum part in light color

We have been trying to anodize a cast A380 aluminum part with a light brown, light green color with no success. All the samples received back from the plater are dark grey-ish looking and does not meet our specs. The plater tells us that there is no way to get a light color finish on these castings. Does anyone have any additional experience with this and found a way to do it or am I out of luck. Any input is appreciated.
Pascal Barth

2006

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Change your spec to call for a dyed anodize finish. Be forewarned that you will get many pieces that will have an uneven color. Reason, it is a cast alloy and if I remember correctly, it is a high silicon one. If that anodizer can not give you the colors that you want, shop around as there are a number that will come close to what you want , for a fee.
James Watts
Navarre, Florida
2006

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2006

You anodize "aluminum", you do not anodize "silicon" which is very high in 380. So you must reduce the area of silicon on the surface and increase the area of aluminum. Most job shops are not set up to do this and they just run the die cast right through the wrought line deoxidizer.
380 varies from caster to caster, and is most worst with thin walls. Make-up 50%/vol Nitric Acid with one pound per gallon ammonium bifluoride, after cleaning, dip the part in this until it turns frothy white all over, about 20 to 30 seconds, then anodize - that is the best you can get with that particular casting.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina