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New To Anodizing

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  • New To Anodizing

    Hiya guys, hope you can help answer a few questions, I am new to anodizing!.

    I am from the UK and will be gathering my own kit, very basic at first, but then develop it!.

    I want to idelly start a sideline in anodizing car bits n bobs (throttle bodies, alternator casings etc), maybe even bigger Cam Covers etc oneday.....

    I intend to use a storage box (plastic) as my anodize tank, with two aluminium sheets as cathodes at each end (8x8 i expect). Battery acid 1/4 and 3/4 dionised water as my electroyte.

    A Car battery charger will be used as my power supply.....and for now I will be using fabric dye to dye components, although if i get "good" results, ill look at upgrading to a propper setup (before doing things for other people), with Caswell dyes.

    I have 3 main questions that would help me get started!

    1) One of my peices i plan to anodize has 3 mild steel fixings in it, can i dip these anyway, i know they wont get anodized, but they cant be removed . OR will they wreck the peice?

    2) If you use Aluminium Cathodes, dont they anodize too and have to be replaced (due to loss in conductance?).

    3) Current Density. I dont really understand how to work out timings, I have seen the 720amp minutes thing, I assume I have to start the peice going, read the current draw, and then work out the time required based on surface area? As i wont be able to control the current much (battery charger), so I assume i must read the current first and then calcultae timings?

    Many thanks in advance

  • #2
    Although you in the UK may not have all the facilities of the USA Caswell setup, you should, at least, download and follow the anodize instructions.

    As for using fabric dye, well, don't come here for support please. Our UK distributor has a stock of dyes, and can get more if you simply ask.

    Better control that battery charger, and don't use any other instructions other than those on this site.

    If you 'get with the program' we offer, you will get support from this forum.
    Wing it on your own, and you will surely fail.
    Mike Caswell
    Caswell Inc
    Need Support? Visit our online support section at


    • #3
      Thanks mate....didnt realise you had a UK distributor.....great news, do you have any contatc details?

      Many thanks


      • #4
        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

        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.


        • #5
          The plastic tank and aluminum plates will work fine. Make sure that you thoroughly clean the plastic container to remove any oils/dirt/grease that may be imbedded from manufacturing. Same goes with the aluminum plates. Some manufacturers, depending on what original use the plates where intended for, even coat their aluminum with a very thin coat of plastic, so you have to make sure you scrub all that off too. If you are just using this setup to test, the aluminum will work fine, but in most cases you'll probably want to change to lead plates. They are easier to work with and don't require constant cleaning like the aluminum plates.

          Deionized water should be fine, as long as you are sure it also is free from any mineral or chemical contamination. If not, use distilled.

          A battery charger has been know to work, as long as it is NOT an automatic charger and the piece you are anodizing is small enough that the voltage and current provided by the charger are not exceeded. Battery chargers are not really recommended, but if it as you have to work withe and you should review many of the posts here that apply to them. The link that scocklin provides has information on a circuit you will have to build and add to the charger so that you can control it for anodizing.

          If the piece you are anodizing has steel fittings, you can't anodize the piece. The acid will dissolve the fittings, and it will contaminate the electrolyte solution. Depending on the fittings, you may be able to mask them in some way, but you will still be running a risk if the mask leaks.

          Aluminum cathodes don't anodize. They are on the 'cathode' side of the circuit and only the 'anode' side anodizes. They do, however, tend to become covered with scum and salts and do have to periodically cleaned.

          scocklin has described the current density. My only addition is that you anodize at 6amps per sq/ft as opposed to 4.5amps per sq/ft. Althought 4.5 works fine, from testing I've found that 6amps has a better success rate.

          Edited to add: Don't even think about using fabric dye. You'll get very little support here if you have problems (very little = none). Fabric dye has been known to work, BUT, not very often or reliably. Also, being organic, it fads rapidly in sunlight. I don't know the prices for fabric dye around you, but around me, comparing the price to make a concentrated solution of it and the cost of anodizing dye, its not worth the few pennies saved. Stick with anodizing dye.


          • #6
            Many thanks, I have found the UK Distributor for the dyes, I shall order the blue!.

            How do you go about getting constant colour matches between parts?

            I am assembling a case for an electric item (car ecu), and due to the size of the tank i can only really do one thing at a time I think.....just make sure I dye each part for the same length of time?

            Is it easy? I dont want to have lots of differing panels!


            • #7
              Assuming that you mean no discernible difference in color or shade, its not that easy. It will require more than just the same dye temperature and time.

              Best matching will occur when all of the parts are made of the same alloy, and have the same surface prep. Producing an anodize layer of consistant thickness and pore density among all of the parts will also be required. A consistant layer will require tight control of the current density for each part; which mandates accurate current control (a CC/CV power supply) excellent electrical connections, consistant anodizing temperature, and consistant electrolyte agitation.

              Very dark colors are the easier to match (except green and red) with black being the easiest by far.

              On a more basic level; using a tank and electrolyte volume that is substantially more than is needed for the part makes temperature control easier, using a cathode distance substantially larger than prescribed 3 inch minimum also helps.


              • #8
                Just ordered the Blue 4A dye from the UK Caswell distributor

                Cant wait, Andodizing tank is setup, will be using 10% Sulphuric Acid (due to not being able to find battery acid!). As my electrolyte.

                I really need to find a CC Rectifier I think, battery charger just wont cut it.

                Will let you know how I get on.

                The Ally is all the same, sheet stuff, it is olted together to make a box.....(ECU Case), so I am hoping to get the same blue on all the peices, fingers crossed. If Anodizied and Dyed for the same amount of time it should be!