Welcome aboard PhilM, first I have to explain the importance of this forum. If you start by reading through past post and using the search function for specific question allot of your questions will be answered. I am a newbie also and after two months of study and questions to the forum moderator (Fibergeek) I have been able to achieve excellent results.
The procedures Caswell, Inc have put together for Low Current Density Anodization (LCD) are as far as I’m concerned flawless. Purchase their manual, read it and don’t deviate from it.
I not sure if the specific gravity of battery acid here in the U.S is the same as England but I assume it is. LCD anodization requires a 3 to 1 ratio mixing 3 parts distilled/de-ionized water to 1 part battery acid and remember to Always Pour Acids Into Water! The Caswell manual will give you the specifics as to the mixing ratio of battery acid to water.
I use 8”x8” lead plates purchased from Caswell but I have read in various posts in this forum that aluminum plates also work well. I know that aluminum sheeting sold here in the U.S. at hardware stores used for flashing roofs may have some type of plastic coating applied that will have to be removed.
I am in no way connected to Caswell Inc, other than they do have my credit card number on file. So I’m not trying to promote their products in any way to my benefit. But their stuff does work usually on the first try. Before attempting to anodize aluminum I read through the form as to using a battery charger. What I found was allot of failures where occurring using those chargers. The Caswell manual does explain how to hook up a charger to your work using light bulbs and load resistors, But I decided to purchase a constant current power supply for my LCD work and have had no problems as of yet. The CC power supply has digital readouts for current and voltage. You can set your current for the size of your work and the current will hold at the point you set it at. You can than watch your voltage and determine where and when you hit peak voltage. The forum moderator Fibergeek can further explain this to you. Also connections are very important; I purchased the Sput Welder and use it without any connection problems. Read the sticky at the top of this forum on the “Importance Of Good Connections”.
I have anodized aluminum with stainless steel parts attached without problems. You can mask the steel parts if you like. The only thing that will anodize is the aluminum.
The 720 rule is a guide line as to how thick of a coating do you want to anodize on you aluminum work. If you anodize a segment of aluminum 1 inch wide by 10 inches long and 1/8 inch thick you should first calculate the surface area of the piece.
1 X 10 = 10 square inches x 2 for both sides = 20 square inches. 20 x .125 (thickness) = 2.5 square inches. 20 square inches + 2.5 square inches = 22.5 square inches.
The surface area (SA) of your piece is approximately 22.5 square inches.
Start off anodizing at 4.5 amps per square foot. Break this down to amps per square inch. 4.5 / 144 ( 4.5 amps divided by 144 or 144 square inches in a square foot) = 0.03125 amps per square inch. Multiply 0.03125 by 22.5 and you get approximately .7 amps or 700mA.
If you’re using a CC power supply you would set your current for 700mA and time it for 90 or 120 minutes depending on the thickness of your coating you’re going for. Do a search on the 720 Rule for more on thickness coatings.
For more on LCD go to
www.caswellplating.com/kits/lcd_ano.pdf
Stay away from fabric dyes! Use the metal dyes that Caswell sells. I spent a week reading through the forums and trying various methods in order to get good constant results using professional red dye. If you want good results and dyes that retain their color stick with the professional stuff!
Most important do a search on cleaning and preparation of aluminum before you anodize. You can also do a search on various posts from an expert metal finisher who goes by “M_D” on this forum. He has some excellent tips on how to prep your work for anodizing.
I’m a middle aged white bearded guy that has learned allot from my mistakes. One thing I have learned is go with what has worked for others. LCD Anodizing is a somewhat simple science that works by the numbers. Learn the numbers follow them and you will have great success. Post your questions on this forum for any difficulty you may run into. I hope this has answered some of your questions and has given you a general understanding on where you have to go from here.