Anodising at home.

[mattthemuppet2]

I use sodium bisulphate and it works just fine. A nice thick oxide layer will give the piece a faint gold tint. Cleanliness is key (scrub with dawn, then acetone, then isopropanol, then do a water break test) and good dyes are a must.

 

[th62]

You have to state whether the concentration is weight/weight or volume to volume. When I worked in an analytical chem lab back in the seventies, we used a dilution of 1 part sulfuric acid to three parts water which is a 25% v/v. solution. Sulfuric acid has a sp.gr. of 1.83 so this would be a 38% w/w solution. I noted at the time that this was very close to the concentration of battery acid. Thinking about it, maybe we used that concentration because I worked for a battery company?

A 19% w/w concentration would be an 11.4% v/v concentration. It is simpler and safer to dilute acid by volume rather than weight. I dilute battery acid 1 part acid to 1 part water by volume for anodizing.

Ditto.

 

[RJSakowski]

You can buy sulphuric acid, or you can buy battery acid. I stated, very clearly, I used battery acid. If you buy battery acid it is clearly labelled on the container it is 35 percent sulphuric acid. I don't know what lab you worked in, but dilution rates are measured by weight, not volume. However, the dilution rate is not super critical.

I have a degree in chemistry and my first professional job was as an analytical chemist for a national battery company. My 43rd ed. of the CRC Handbook of Chemistry and Physics, pp. 1664, has a page devoted to dilution of acid by volume for sulfuric, hydrochloric and nitric acids.

Diluted sulfuric acid solution can be purchased by either w/w or v/v. Fisher Scientific, arguably the largest chemical supplier in the US, sells in both forms. Here is one example. https://www.fishersci.com/shop/prod...on-for-phosphorus-spectrum/18614261#?keyword=

Acids are often diluted v/v because of the relative danger involved with weighing out concentrated acids. If the dilution method is not specified, w/w is implied. For precision work, we always used moles/l. as there is some additional ambiguity as to whether the method used was based on the volume of reagent to the volume of water as in the Fisher example above or the volume of reagent to the final total volume since for most chemicals, the the volumes aren't additive.

As to my original post, actually, we are saying essentially the same thing. My 1:3, 25% v/v solution is 37.89% by wt and diluting that 1:1 v/v is 22.8021.12% by wt. This is in the ball park for anodizing. As you stated, the dilution rate is not super critical.

Edit: I used the wrong sp.gr. in calculating the final concentration. in the above paragraph. The 21.12% by wt. value is the correct concentration for the anodizing solution that I used.

 

[RJSakowski]

Well, if you have a degree in chemistry you should know that acid and water do not weigh the same, that is why, dilution rates are measured by weight not volume.

I am fully aware that there is difference in density of different liquids. I am also proficient in all methods of dilution of liquids, having done so for almost sixty years.

Dilution of liquids by volume is common. Antifreeze, fuel for two cycle engines, machining coolant are all done by volume. Biochemists do serial dilutions by volume to make up their standard series. Most agricultural chemicals are diluted by volume.

As to dilution of acids, here is a page from "An Introduction to Semimicro Qualitative Analysis", 1sr ed. by c.H. Sorum. This text has been a standard for collegiate chemistry courses for over 70 years. All the acids and the liquid base, ammonium hydroxide, are diluted by volume.

 

[mattthemuppet2]

p!$$ing matches aren't super helpful to be honest, it would be much more useful to focus on anything that might help the OP or anyone else who's reading. That is if the OP wants any help or if this was more of a "look what I did" post?

 

[mattthemuppet2]

I think you're arguing with yourself mate, everyone else has left the room.

[moderator]: to avoid confusion, the improper and slightly abusive posts by th62 have been deleted as obstructive to the thread.

 

[Dabbler]

The OP, Th62 posted this at the top of the thread, edited:

This post was meant to show anybody thinking of doing some anodising how easy the process is. I am by no means an expert, however, my technique follows that of 'anodising' professionals. I want nothing more to do with it.

I have locked this thread as it appears that it has caused hard feelings. Anyone wanting to comment or for more information, PM @Dabbler