Selection of rectifier / how to get shine in anodize

A. Hello Madhav.

Start with a rectifier rated for 25 amps per square foot and 18 volts, with ramp control. You probably won't need quite the full amperage and voltage stated, but you don't want an oversized unit and you can't do the process with an undersized one.

Anodizing does not add shine, it somewhat reduces it. You need to polish and/or bright dip the pipe before anodizing if you want it to be reflective. Best of luck.

A. Hi, Madhav. Conventional sulfuric acid anodizing (Type II, not Type III hardcoat) usually takes place at a terminal (final) voltage somewhat less than 18 volts and at a maximum current of somewhat less than 25 amps per square foot. This depends to a degree on what alloy you are anodizing. My reply is empirical, based on experience, because trying to calculate it based on the resistance of the anodizing film is probably beyond our current understanding.

But please don't try to "purchase right" from these forum replies; the replies are for general education and discussion only; they are not purchasing specifications. You should purchase rectifiers from experienced suppliers who understand the requirements for ripple management, ramp control for anodizing applications, and robust design for shop floor application. You'll find such suppliers in ourDirectories here, and locally through plating chemistry distributors.

Best of luck!

A. Hi Nitesh.

So that we can keep moving forward, please try to phrase your questions in terms of the answers that were already provided. When you simply repeat questions that were already answered, we have no idea what you understood and didn't understand. Sorry.

You need to know the surface area of the parts that you will be handling simultaneously (as one load):
You will probably be anodizing at 18 to 20 amps per square foot, but I suggested multiplying that surface area by the slightly larger number 25 to get a good idea of the required amperage of the rectifier. Again, the voltage will depend upon the alloy you are anodizing, varying from perhaps 12 to 16 volts, but a rectifier that can produce 18 volts should prove adequate for all alloys.

It is essential that the rectifier have "ramp control":
By the time you are finished anodizing, it will take that 12 to 16 volts to achieve the necessary current because the anodized coating is insulative/resistive. But when you first start anodizing upon a conductive aluminum surface, the voltage must be very low or the current will be excessive and will burn the parts. "Ramp control" means the voltage starts out very low and gradually ramps up as necessary to maintain the desired current.

Please find a firm that sells anodizing rectifiers rather than trying to explain what you need to an inexperienced supplier.

As previously noted, anodizing does not add shine, it slightly reduces it:
You must mechanically polish, electropolish, and/or chemically bright dip the components to brightness before starting the anodizing. Then you need to optimize the anodizing process to minimize the reduction in shine (by avoiding etching, minimizing desmutting, keeping the anodizing as thin as practical, and with high quality sealing.

We'll be happy to keep trying to help, but you must phrase your questions in terms of these answers, so we have some feedback about which words and phrases and concepts you are understanding, and which you are not yet understanding. Good luck!

Regards,