Best anodizing guide?

[JOGARA]

How long are you actually leaving it in the dye for? In the videos it seems you are just doing a very quick dip, I was of the understanding that it’s more like 15mins.

Are you going straight from anodising to dying after a rinse with distilled water?

If it isn’t accepting the dye, in my very limited knowledge I would say it can only be a few things - either the anodised layer isn’t sufficient (poor connection/insuffficient power supply/not long enough in the run), or the pores are too small

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What solution strength have you got and at what current per square foot are you doing it?

I have left it in for 20-30 mins and even an hour. Same result as putting it in for 20 seconds.
Yep Anodizing > Rinse > Dye > Seal
Have not got to seal yet though...

I have directly connected my alligator clips to the part and it still didn't accept the dye. The power supply is 48V 5A so plenty and I have left it in for 2+ hours yesterday.

I believe my solution is around 20-25% acid to water.
My acid was only 85% though so I might add some more.

Calculated for my part 25V max, 2.7A for 72 mins.

[chas-SX3]

I have left it in for 20-30 mins and even an hour. Same result as putting it in for 20 seconds.
Yep Anodizing > Rinse > Dye > Seal
Have not got to seal yet though...

I have directly connected my alligator clips to the part and it still didn't accept the dye. The power supply is 48V 5A so plenty and I have left it in for 2+ hours yesterday.

I believe my solution is around 20-25% acid to water.
My acid was only 85% though so I might add some more.

Calculated for my part 25V max, 2.7A for 72 mins.

Is your part electrically conductive across its surface after anodising?

[chas-SX3]

When you say your power supply is 48v 5a . . . . Exactly what power supply is it?

You MUST use a power supply where YOU set the amps it's putting out.

[Zeeflyboy]

Calculated for my part 25V max, 2.7A for 72 mins.

Sounds like he is using a constant current supply if he is able to set 2.7 amps... I assume you are using 6 asf and then using your cad program to determine surface area of the part multiplied by the number of parts being done at once to arrive at the result?

From my research I've seen suggested that for 6 ASF you are looking at something around 1:15 acid to water ratio (6.7%), so actually if anything yours sounds significantly too strong. Caswell only mention battery acid (usually around 32%) at 3:1 with their 4.5 ASF, so unless my maths fails me that would be an actual acid/water ratio of around 1:11 or roughly 9%, again making your mixture far too strong if using their 4.5asf method. Oddly enough that should result in a larger pore size however... perhaps you actually end up with pores too large to hold on to the dye? Conversely the excess acid concentration may mean that it is breaking down as fast as it builds up, leaving you with an insufficient anodised layer.

I would suggest you adjust your solution to the correct strength and see how it goes.

Also don't submerge crocodile clips into the bath, no metals other than the lead/alu cathodes and alu/titanium wires/rods should be in contact with the acid solution. Other than potentially contaminating the bath, the current will try to flow through the steel clips instead of the aluminium and your anodising will stop.

[JOGARA]

I have a DPS5015 so yes can set max current and voltage.

I had use use STL to surface area calculator http://preview.codecanyon.net/item/3...762.1508073459
Then metric to imperial and used this 720 calculator http://www.ndhsubmersiblescience.com/ano/720rule.html

Worked out to the 25V max, 2.7A at 72 mins for my parts.

My clips are not in the bath, I read about the problems with contamination.

I think ill split my tank in 2. Then add 1L to one of them and see if that is okay.

[Zeeflyboy]

What cad program are you designing in? I can't imagine you need to use an STL to surface area calculator, should be able to pull that info straight from the CAD program.

How big is your bath? Will splitting in two and diluting with 1L bring you to something under 10%?

[JOGARA]

What cad program are you designing in? I can't imagine you need to use an STL to surface area calculator, should be able to pull that info straight from the CAD program.

How big is your bath? Will splitting in two and diluting with 1L bring you to something under 10%?

Fusion 360 but can't work out surface area for some reason.

I have 5L tubs. Only 3L of water plus added ingredients.
By weight I have 3000g of water and 400g of 85% acid. So that is 7.5% of 85% acid?

[JOGARA]

Forgot camera was in JPEG >.<
Should be able to see well enough though. This is the part I had in for a tad over 72 mins (by accident).

[Zeeflyboy]

Fusion 360 but can't work out surface area for some reason.

I have 5L tubs. Only 3L of water plus added ingredients.
By weight I have 3000g of water and 400g of 85% acid. So that is 7.5% of 85% acid?

Rarely see suggested ratio by weight, usually by volume.

However, simple enough to figure out an approximation I guess. 3kg of water is 3L, for the sake of simplicity we'll say your 400g of 85% acid is actually 340g (400 * 0.85) and ignore the extra 60g of water, which when considering the specific gravity of sulphuric acid is 1.85 should mean it was about 184ml.

So you have actually got 0.184L acid to 3L water, or roughly a 1:16 ratio which is not too far off what I've seen recommended for 6asf (slightly low perhaps), but more than a little on the low side if using 4.5asf (caswell recommend 1:3 battery acid/water, or around 1:11 acid/water if my maths holds up).

That jives more with what you would expect - too low a concentration will give a smaller pore size which is bad for dying. Were you calculating with 4.5asf or 6asf out of interest?

[Zeeflyboy]

Oh and fusion will give you surface area very simply - just use the menu on the left, select the body in question and right click - properties. First property is area.