Three more questions about anodizing

A. Hi Madhav.

1. There is no need for lead. The tank can be polypropylene and the cathodes aluminum if you prefer.

2. However many kilowatt-hours of power (voltage x amps x time) your rectifier puts into the tank, your chilling system needs to remove or the temperature will rise, which will cause unsatisfactory anodizing.

3. Sorry, I don't know enough about it to comment on pricing issues. Plus some people feel public posting of pricing information leads to collusion, and that's not legal.

A. Hi again, Madhav.

1]. You don't use concentrated sulfuric acid in anodizing, you use about 10 percent by volume. Aluminum cathodes are widely and increasingly used.
2]. I don't understand this question. The bus bar is the current carrying member which brings power from the rectifier to the work and to the cathodes. Yes, it is required.
3]. I don't believe there is any such chemical. Anodizing baths need to be chilled.

There are many subjects about which I know absolutely nothing, so please don't take offense, but based on your inquiries on this letter, and letters 30208, 30119, 30071, and other letters here, it appears you don't yet have much background knowledge of anodizing, and I am concerned that you might attempt to build an anodizing plant with no other information source except our answering questions here :-)

That's dangerous because if you don't know the questions to ask, I may be leading you astray. If you can't hire a consultant to help get you started, please get some books about anodizing, starting with Robert Probert's "Aluminum How-To", then proceeding to our "must-have book list" and our links to metal finishing books from Amazon.

Thank you for your visits, and for your offers to help others in return! ... but the very first thing one needs to build as part of an anodizing plant is a small shelf of anodizing books :-)

Best of luck!

A. Solid dihydrogen oxide [Ice] :-)

A. There is no such animal. There are additives that let you do a pseudo hard coat at a temperature higher than 32 °F but it still requires chilling to maintain that temperature. Regular Sulfuric anodizing requires chilling to maintain the selected temp ±2 °F or you will have a very different output (BAD!), which will cause you great grief from your customers. Buy a properly sized chiller and forget trying to anodize on the cheap.

A. We'd all like to avoid the expense of anodizing chillers, Mr. Sakhare, however, as Ted said, and also to my knowledge, they are a necessary evil. I believe this, and several other letters you've written are exactly what the latest editorial page/comments are referring to, please take a minute to read it.

A. Dear sir!

There is other solution for hard anodizing and which require higher temperature I can suggest you one from a book, I never tried. Oxalic acid 25 g/l+citric acid [on eBay or Amazon] (lemon acid)25 g/l. 2 am/sq.dm/temperature 45 C/30 minutes thickness approx. 30-40 micron. One thing you should count -type of your alloy may require some other solution and conditions.

Hope this helps, good luck.

A. The vast majority of hard anodising is done at temperatures very close to the freezing point of water. This is a fundamental feature of the process. When you pass electricity through an electrolyte it gets hot because of the resistance of the solution combined with either the voltage or current. Basic Ohms Law relates resistance, voltage and current. The product of volts and amps tells you how much energy is going into the system and this energy has to be dissipated as heat. You now have a problem, where you are putting heat into a system that you must keep cold. Fundamental thermodynamics tells you that something has to be done to get around this problem. The only way to do so is to take the heat out of the system. That is why you will need a chiller. Unfortunately Mumbai is probably not the best place in the world to keep things cold as it is so hot there! To reiterate what Ted has said, there is no chemical additive available that will take heat out of an anodising system - you MUST use a chiller or your "anodised" work will be useless.

A. Thank you for your visits, Madhav. You have certainly hurt no one. I have simply suggested that you obtain a couple of books about anodizing.

A. Oxalic Acid or not.... the bath will still need to be chilled, and kept at a constant temperature, in order to produce a quality product. I think you are being misinformed if you are told that oxalic acid will "cool" your anodizing tank.

A. Dear Mr Sakhare,

Just a note to inform you that not all consultants and anodisers are looters as you have generalised in your letter. Probably you were unfortunate enough to have ended up with a quack else your expectation from the said consultant might have been unreasonable (How to do anodising without chilling and electricity), etc.

Warm regards,

A. Hi, Pramod. The chilling capacity is equal to the heat input, which is the amperage of the anodizing process multiplied by its voltage, multiplied by the "duty factor", which is usually equal to one. What is required in hardware depends on the temperature. The chilled water must be perhaps 7 degrees °C lower than the tank temperature, and this may require that the chilled water circuit contain a water glycol mixture to prevent freezing.

Tell us about the anodizing parameters and we should be able to give the chilled water parameters. Good luck.

Regards,

A. Hi Ted and all you guys out there,
I have been following finishing.com for the past few months now and it has been a great resource of practical information. I help in my dad's anodizing plant and I think it is the best job in the world.
I happened to read some of the responses to your replies and I must agree with you that books are the next best thing to practical knowledge, experience and advice.
There are many people in Mumbai who would definitely impart good knowledge when asked. Some firms which deal with rectifiers and chemicals have people trained in the various forms of electroplating and help is generally offered for free on purchase of chemicals or equipments from them.
I hope this helps.
Best regards,