Trouble getting Sand Blasted Aluminum to take color.

[LogicPB]

Here is my problem:

I am anodizing 6061 T-6 Aluminum, that has been sand blasted, and I am having trouble getting it to take color.

I am using the Caswell Deep Red color dye.

I first washed the part well, mounted the elctrode wire, then I soaked the part in a mild Nitric Acid solution, and after a rinse, it goes into the bath.

I anodized the part for 45 mins, washed it again, and then into 130 deg dye. I let the part soak in the dye for 15 mins, and then boiled them for 40 mins.

When that was all done, I am left with a part that has a slight reddish/purple twinge, with an overall grey tint.

What am I doing wrong?

I have gotten a glass bead blasted part to take color, albeit a different one. (Caswell Electric Blue)

Is my red dye bad? I haven't been able to get a good red on any part, bead blasted, sand blasted, or gloss. It always goes pink.

I have fortified the dye, thinking it was just mixed too weak, but with no result.

Any help would be greatly appreciated.

I know this can be done; I have seen it, I just don't know how to make it happen.

Thanks for your time.

[LogicPB]

Here is a pic of the part with the funky red color.

The color is more dull and grey if you look at it in your hands, but the flash kinda washed out the greyness.

Here it is:



Thanks again.

[mcaswell]

Have a quick read of our anodizing instructions at http://www.caswellplating.com/kits/aluminum.htm. There are a lot of factors during the anodizing process that can alter the color of the dye. Temperature of the bath and current applied all affect the pore size, which affects how well the dye is accepted. Too large a pore size and the dye bleeds out; too small and the dye can't penetrate.

[LogicPB]

Thanks, I'll give that a read.

I'll post again after I have made another attempt.

Thanks again.

[Tim Wiltse]

Logic,

First are you sure is 6061? Some other alloys will "smut" real bad and the gray tint is what it looks like. Second being that you are blasting your parts first will make them have a different finished color due to the ruffed up surface. Third don't boil to seal, hang the part in the steam. You are losing alot of color by boiling it out of the pores before they can seal. Fourthly( is that a word?) what temp is your anodizing bath at when you are running your parts? To warm and the pores are to big and don't hold color.

Hope this helps,

Tim

[LogicPB]

I think it was the bath temp.

I am sure it is 6061, I buy my bar from a reputable dealer, and it is labeled very well.

I have done blasted parts before, with good results, just not red.

I re-did the "pink" frame today, and the bath temp was a bit lower. (Cooler outside)

It held its color better, but I also used a different dye.

I used to steam my parts, but that led to streaking, the boiling gives me a much more consistent color.

Thanks for all your help guys, I really appreciate it.

[fastmerlin]

I think the problem is when you sandblast a part you increase the surface area from that of a polished surface. I have found that I have to almost double the time I calculate when my parts are blasted. I have also found that keeping the temp. between 65 and 75 is very important. As you get into parts with larger surface areas the temp,power supply etc, become more critical.

[24Seven]

Also try the NEW low temperature sealers for anodizing offered here. This is used after the color is applied. Reds always have more of a tendancy to bleed in many other non related process, and do not know if that would in fact be the same case here as I have not as of yet done any anodizing. BUT... I did read on the link from one of the customers of Caswell who builds telescope parts mention the better success he had with these lower temp sealers.