HARDCOAT ANODIZING SYSTEM
TYPE III
Chemicals and Equipment To Setup A Hardcoat Type III Anodize Line
Contains:
• 3 x 6 Gallon Tanks (for Degreaser, Desmut & Anodize Baths)
• 1 x 8.5 Gal Enamel Tank (for sealing)
• Aluminum Degreaser Powder
• Deoxidizer/Desmut
• Anodize Sealer
• GP Plates (cathodes)
• Titanium Wire For Hanging Parts
• Mist Suppresstant
• Rinsing Bottle
• 30 Amp/30 Volt CC/CV Rectifier
You Will Also Require:
• 1.75 Gallons Battery Acid (most automotive parts stores sell this)
• Chiller System (check Aquarium Stores)
• Tubing & Pump To Run Chiller
HARDCOAT ANODIZING
The process of anodizing is, chemically speaking, rather complicated, but in practice is extremely simple.
The process involves placing aluminum in an electrolyte, weak sulfuric acid, and passing a low voltage current
through it. The aluminum part is connected to the positive (anode) side and the negative side is connected to a
cathode made of lead. This causes the aluminum to oxidize, similar to steel rusting, with the net result of a very
hard, tough abrasion resistant protective coating being formed. An interesting 'quirk' of this process is that the
film formed looks like honeycomb, and has 'tubes' growing up from the aluminum.
For the technically inclined, the surface of the aluminum actually
grows a layer of aluminum oxide on itself, which is then transformed into aluminum
hydroxide (anodize) and finally hydroxide monohydrate. The whole anodize layer is non
conductive. The hydroxide is microscopically porous which allows it to absorb dyes. This
layer looks somewhat like a honeycomb, as can be seen from this photo, magnified some
40,000 times.
The 'barrier layer' at the base of the pores is thin enough to pass some current, even though the
complete layer is non-conductive, so the honeycomb structure continues to grow, as long as
current is flowing through the system. The acidity of the solution will also dissolve the anodize,
so the latter is only true if dissolution is not faster than growth.
Looking from above
Cross section
Hardcoat Type III vs Type II
Type III anodizing is a much harder coating than Type II. It is commonly seen when strength and lubricity is of the upmost importance.
The Type III layer gets its strength from a more condensed pore structure than Type II. This is achieved by anodizing at very low bath
temperatures. This also means that it will not readily accept dye. The pore structure is too tight to absorb color.
Setting up the Anodizing Tank
Wiring up the parts.
Anodizing requires special attention to wiring up the pats, because
only aluminum parts can be placed into the solution, so the actual
wire, must be made of this, or titanium. Consequently, an aluminum
wire also is anodized. If a connection is poor, then the anodize film
grows on the wire, where it is touching the part, and an insulating
barrier is formed, preventing further film growth.
Titanium wire is supplied in all the kits, and can also be obtained
separately. Thin aluminum wire may be obtained from almost any
garden center/hardware shop. This is ideal for wiring small parts,
as long as you make sure you secure the wire mechanically, either
by wedging it into a hole or by tightening an aluminum bolt onto it,
and into the work piece.
2
Ideally, the tank bar should also be made plastic. This will avoid corrosion problems and any shorting out due to mists settling on a
metal tank bar. A solid bar of plastic could be used, and for the engineering inclined, this could be drilled with holes to accommodate
the wire or needle, which could be secured with hex head bolts, tapped into the block.
An alternative technique to wire is to use
knitting needles. By removing the top of
the needle and bending it into the shape
needed, it can be forced into a slightly
smaller hole, using the needle’s tapered
point as a wedge.
Aluminum knitting needles are usually anodized, and as this is an insulator, the anodize must be removed, either by
sandblasting, abrading with emery paper, or stripping in the anodize stripper. If stripping, leave the needle in the
stripper until all the color has gone, usually about 3 minutes. Some needles are coated with lacquer, so you may have
to abrade this off.
If you decide to re-use these, you MUST strip off the anodize film every time prior to usage.
Knitting needles (see left) are usually made of harder material and so, when the taper is forced into the hole, it
slightly enlarges the softer aluminum, ensuring a tight fit. Soft wire will actually decrease in size if pushed into a
work-piece, which is harder than itself, thereby shrinking it, and causing a loose connection.
There is a host of different types of Titanium grips and racking clips available. Titanium is actually better than using
aluminum, as it is not anodized in the process, saving you the job of stripping your racks after each operation.
Titanium is also much harder and stronger than aluminum.
Servi-Sure Inc are suppliers of these racks. www.servisure.com
2020 W. Rascher Ave., Chicago, IL 60625 Phone: (773) 271-5900, Fax: (773) 271-3777
Email: racks@servisure.com
Installing the GP Plates (Cathodes)
The anodizing system uses 2 GP plates 8" x 8" as cathodes. (The actual part
being anodized becomes the anode). To install these into the tank, see page 11
& 12 for anode/cathode installation procedures.
The GP Plates should be occasionally cleaned using wire wool or Scotchbrite type material.
Remove the plates from the solution when not in use.
3
CONTROLLING THE POWER
The Power Supply and Power Requirements.
Unlike plating, anodizing has the peculiarity of becoming an insulator to itself, cutting off power and stopping further growth of the
film. The thicker the film, the more insulated the part becomes from the power supply. There comes a point when a Peak Anodic
Resistance (PAR) is reached, when the film will grow no more, and if power is kept being applied, it actually erodes away the film.
PAR is quite visible on a rectifier, because the amperage needle drops off. It is therefore useful to install some type of ammeter into
your system, so you can see when you reach PAR. The optimum current requirement is 4.5 amps per sq foot, or 30 milliamps per sq
inch. This can easily be supplied from a 12 volt battery and controlled using light bulbs.
See the FLASH VIDEO on www.caswellplating.com concerning controlling the power with light bulbs.
a. Battery chargers
Battery chargers do a good job on anodizing, but the
current still needs to be controlled. Using light bulbs
will do this economically. Set the charger to the 12 volt
position.
There are some major misconceptions about using battery
chargers as power sources. Battery chargers are rated for
driving a partially discharged battery, not a grounded load
like anodizing or plating. As an example, the voltage was
measured and current of a charger under load. This unit was
rated for 12V at 10A, when loaded the results were as
follows:
• At 0 A (no load) V=13.4 V
• At 3.66 A (3 Ω) V=11 V
• At 5.35 A (2 Ω) V=10.7 V
A 10 amp load wasn’t tested as it would overheat the charger and open its thermal circuit breaker if operated for any realistic length of
time. If this unit were rated as a transformer isolated unregulated power supply, using a full wave rectifier (which is what it is) the rating
would be 10.8 V at 5 A. Larger or smaller chargers will scale accordingly.
Besides not putting out the voltage and current that you
think you are getting, battery chargers also have no
effective means to reduce the voltage and current provided
to the load. You can compensate for the first problem by
de-rating the battery charger as discussed above, and there
is something you can do about the control problem. A
perfectly simple way to solve the control problem is to use
an ordinary 600 W lamp dimmer to control the input to the
charger. This is shown in Figure 6. A charger is a
transformer load, not a motor load. The dimmer can power
a transformer as easily as it can power a light bulb. The
resolution you can actually get isn’t great, but it is better
than you can get using any reasonable number of power
resistors or light bulbs to control the current.
Figure 6. A Variable Voltage Battery Charger Power Supply
b. Batteries.
Batteries are not the best power source for anodizing. You are better off using a battery charger controlled with a light dimmer
switch. Monitor the current using a multi-meter and a shunt 0.1ohm resistor, as per fig 6.
c. Rectifiers.
Rectifiers are the ultimate in anodizing. Variable controls, voltage and amperes dials, allow you to fine tune your anodizing efforts.
Cooling The Anodize Solution
4
To achieve the pore structure required for a Type III coating, the anodizing tank must be chilled down to 37-40 deg F.
While there are many homebrew ways to do this (such as pumping the solution through a cooler full of ice), the best way is to
purchase a chiller.
A 1/4HP Aquarium Chiller should be more than sufficient to chill 5 gallons down to 40 deg F. You will also need an acid resistant
pump to pump the acid from the tank, through the chiller.
We recommend piping the solution from the top of the tank, rather than drilling bulkheads through the tanks. This minimizes the
chance of leaks developing. Acid leaks are not fun.
Make sure to securely attach the pipes to the tank, to make sure vibration doesn’t cause them to slip off.
The WATER BREAK TEST
Also recognised as ASTM-F-22
This test is probably one of the most important procedures in any plating or anodizing operation.
Make sure you carry out this test after doing all the preparation work, including degreasing and etching in pickles.
To pass the test water will sheet off the part rather than bead off.
Take a cleaned and dried part and set it in a vertical position.
Use a spray bottle containing distilled water.
Spray the part two to three times from at least 6" away.
If the part is clean and free of oily residue, the water spray should sheet off.
If some oily residue remains, the water will tend to bead on the part
Repeat the cleaning process until the part passes the test.
Alternatively, apply several drops of distilled water to the cleaned surfaces.
If the surface is inadequately cleaned, the spherical form of the drop is largely retained, and the surface must be cleaned
once more.
If the water runs on the treated surface, then wetting has been satisfactory and the part is ready for plating.
Oil/dirt film makes water bead up
No oil/dirt film allows water to cover part
RINSING WITH DISTILLED WATER
The part should be raised out of the solution and sprayed
liberally with distilled water.
The runoff should be allowed to drain into the tank.
5
PROCEDURE SETUP OPERATING EQUIPMENT SAFETY
PARAMETERS
1. SURFACE Buff & Polish for a mirror finish. Bead Blast for a ‘flat’ finish. Nylon Abrasive wheel buff for a ‘scratched
PREPARATION brush’ look.
No agitation 1 x 6 gal tank
5 mins immersion 1 x tank lid
1 x 3lb Degreaser
3lb SP Degreaser
2. DEGREASING 5 gal Distilled water
1. RINSE IN DISTILLED WATER SPRAY
2. WATER BREAK TEST
No agitation 1 x 6 gal tank
3 mins immersion 1 x tank lid
2 x 1qt De-Ox
4 gal Distilled water
3. ALUMINUM
2 x 1 qt De-Oxidizer Wear
DE-OXIDIZER
rubber
gloves and
goggles
RINSE IN DISTILLED WATER SPRAY
37-40 deg F 1 x 6 gal tank
Current at 6 amps per sq ft for 120 1 x tank lid
mins. 2 x GP Plates
3.5 gals distilled water Mist Suppressant
4. ANODIZING 1.75 gal battery acid Chiller Wear
TANK (add acid to water) rubber
2 tsp Mist Suppressant gloves and
goggles
RINSE IN DISTILLED WATER SPRAY
210 deg F on hotplate 1 x Enamel tank
No agitation 1 x 1lb Anodizing
15 mins immersion Sealant
5 gals Distilled water
5 oz Anodizing Sealant
5. SEALANT
Use mist balls and the lid to retain
heat and speed heating. In extreme
cold, wrap sides of tank with
bubble-wrap & duct tape.
RINSE IN DISTILLED WATER SPRAY
6
Aluminum De-Oxidizer & De Smut.
Aluminum De-oxidizer is a concentrated, easy to use liquid material designed to
deoxidize and de-smut aluminum prior to anodizing and chromating. Aluminum De-
oxidizer is non-chromated, yet offers performance comparable to or better than most
chromate bearing products. The product is especially useful on certain types of
aluminum alloys found on Japanese motorcycles, which have a certain amount of zinc
in them. The prescence of zinc makes the casting smut as soon as it enters the anodizing
tank. Pre-dipping with Aluminum De-oxidizer reduces this problem.
PRODUCT FEATURES
No chromate disposal problems.
EQUIPMENT
Tank: HDPE Plastic tanks
Agitation: Continuous air agitation is recommended to increase effectiveness.
OPERATING PARAMETERS
Concentration: Mix 1 qt (1 liter) of Aluminum De-oxidizer with 2 gallons water
Temperature: 70-110°F Optimum 100 deg f
Immersion time: 1-3 minutes
Water: De-ionized or distilled
SOLUTION MAKEUP
Before making up or replenishing the working solution, refer to the Material Safety Data Sheet for protective safe handling measures.
1. Fill tank 2/3 full of water.
2. Add required amount of Aluminum De-oxidizer to the water with mild agitation.
3. Add water to operating level and mix again.
4. 110 deg F
To prevent excessive heat generation and spattering, never add water to Aluminum De-oxidizer. Always add Aluminum De-oxidizer
to water. Add in small amounts over the entire surface of the solution with mild agitation.
Dip the parts into the solution for 1-3 minutes, rinse in fresh water, then immediately proceed to anodize the part.
Operating the Anodizing System.
1. Check the part for cleanliness. After thoroughly preparing the part, by bead blasting, polishing etc. ensure it is completely
degreased by using the 'water break test'. Simply run water over the part, if the water sheets evenly, then the part is clean. If it
'balls up' or spots, then it needs further cleaning. At this point, the part should already be wired up to the tank bar. This will
prevent you from handling it. DO NOT TOUCH THE PART FROM THIS POINT UNTIL THE PROCESS IS COMPLETE.
2. Caustic Etch. Dip, for a few seconds only, into a room temperature solution of Anodize Stripper, as the
etching action will dull the finish slightly. To maintain a bright finish, you may omit this step, however,
the part MUST pass the 'water break test'. Rinse the part.
3. Anodizing De-Oxidizer Dip the part for 1-3 minutes into the pre-mixed solution at 100 deg F. See the
section on Aluminum De-oxidizer.
4. Rinse, thoroughly in fresh water. Agitate the part, and if necessary, spray with water to rinse chemical from hard to reach areas.
A sprayer attached to a faucet is a great idea.
5. Anodizing the Part. Place the pat into the tank, and connect the tank bar to the positive side of your power supply. Make sure
the negative wire is connected to the GP Plates (cathodes). Switch on the power.
6. General Duration of Anodizing.
This is totally dependant on the part reaching PAR, Peak Anodic Resistance) 1-3 hours
Remove the part from the tank and rinse off thoroughly in distilled water.
7. Acid Neutralizer. Make up a tank of 1 gal distilled water and 1/2 lb baking soda, as your neutralizer tank. Before proceeding
to dying, the part must be completely ridden of acid; otherwise, this will cause you problems. Acid dragged from the anodizing
7
tank into the dye tank will cause streaking and blemishes. It will also eventually alter the dye's color. After neutralizing, rinse
in fresh or distilled water.
8. Fixing (or sealing) Using a plastic tank supplied with the kit, place 1 or 2 gals of water, depending on what will cover the part,
and add 1 oz per gallon of ANODIZING SEALANT POWDER, and bring to the boil using the non adjustable ceramic heater.
Then place the anodized part into the tank, using the tank bar as the suspension support. Boil for 2-3 minutes per 0.10 mil.
oxide coating thickness. 24 microns = 1 mil Wipe the parts dry and immediately apply a mineral oil (WD40 etc) with a soft
cloth. Alternatively, you could use ANODIZING SEALANT LT which is a liquid. Add to distilled water at the rate of 2 fl oz
per gallon. Warm the liquid to approx 85-95 degrees and immerse the part for 10 minutes. Anodizing Sealant LT may slightly
effect the color of some dyes, but this is offset usually by the simpler technique.
9. Cure. Allow the part to cure in an ambient, dry area for 24 – 48 hours to obtain its final hardness
10. Polishing. You may polish the part using a loose cotton buffing wheel and either a white or blue buffing compound. Be sure
to take care, the anodize film is not very thick. You could damage it.
8
SEALING THE ANODIZE WITH ANODIZING SEALANT
High Temperature Sealant.
An enameled pot is supplied to heat this solution over a hotplate. DO NOT LEAVE
UNATTENDED or the solution will boil away and the tank may ignite.
Always use distilled water, as ordinary water may leave mineral deposits on/in the film.
Anodizing Sealant is a nickel acetate compound for sealing anodic coatings on aluminum. It is
a fine flowing greenish powder, readily soluble in water and specifically formulated with a pH regulator and an agent to help minimize
smut.
OPERATING PARAMETERS
Make up a solution of : 1 oz per Anodizing Sealant to 1 gal of distilled water - or 7.5 grams per liter
Time: 5 to 30 minutes depending on anodize thickness (2-3 minutes per 0.10 mil. oxide coating thickness) 24 microns = 1
mil.
Temperature: 202-210°F
pH: 5.5 to 6.0
Water: De-ionized or Distilled water
CONDITIONS FOR USING ANODIZING SEALANT
Tank: Sealant solution should be contained in a plastic tank.
pH: pH adjustments will not be necessary unless acidic or alkaline compounds are carried over into this sealing bath. Add
acetic acid (to lower pH) or ammonia (to increase pH). Acetic acid is difficult to come by, and it is preferable to
discard the bath, especially as it has a limited shelf life anyway. White vinegar is a good substitute.
Rinse: Before sealing, a LIGHT rinse is necessary to remove any foreign substances. After sealing, the work should be
thoroughly rinsed at once, as is normal in nickel acetate sealing, before it is dried.
Filtration
Filtration clears the bath of precipitates with interfering action. Filter through coffee filters after each use.
Maintenance. Bath life is 14-60 days dependent upon operating conditions and bath upkeep.
BATH TURBIDITY
Freshly prepared nickel acetate sealant baths are clear green solutions. In use they become contaminated by precipitates and grow
cloudy. If not removed, these contaminants can form deposits on the sealed surface. The effect can be due to the following: High pH
(at pH values above 6.0, nickel acetate may be converted into soluble nickel hydroxide), hard water and trapped impurities.
The following measure can be taken to minimize this affect: Maintain pH value of 5.7 ± 0.3, through rinsing of anodized, dye or un-
dyed work prior to sealing to prevent possible introduction of contaminants and filtration to clarify the bath and to prevent surface
deposit formation
STRIPPING THE ANODIZE FILM
Mix up a solution of 4-6oz of Anodize & Chrome Stripper with 1 gal of water. Add the powder slowly to the water.
Dip the anodized part into the solution for between 20 seconds and 10 minutes, depending on the thickness of the existing anodize film.
9
Rinse off the part thoroughly in fresh water.
TESTING FOR ANODIZE FILM CONTINUITY (see overleaf) and if present re-immerse.
Ideally, the solution should be at approx 70 deg F plus. The hotter the solution, the more rapidly the
anodize film will be stripped. Solution temperature range is 70-150 deg f.
Use only plastic vessels, not aluminum, as this material is extremely corrosive to this metal.
TESTING FOR ANODIZE FILM CONTINUITY
Anodize film in non-conductive, whereas the actual aluminum is conductive.
It is therefore relatively easy, using a multimeter, to determine if we indeed have grown an anodize
film. Set any multimeter to the 1000 ohm setting.
Place the black and red probes on the aluminum in different places. The needle on the multimeter dial will swing over if there is NO
anodize film. If you have grown an adequate film, then the multimeter will not register at all.
The work must be perfectly dry to do this test.
Test does not show ADEQUATE GROWTH, but only that there is SOME growth of film.
Sharp edges can create problems, because the anodize pores grow out at right
angles to the metal. On the example here, the corner area is almost completely
void of pores. This will show up when dying.
MIL SPEC A-8625F calls for a 1/32” minimum radius on corners, when
applying a 1 mil anodize film.
Consideration needs to be given to this phenomenon, and sharp edges should
be rounded over.
Pore diameter and barrier film thickness will vary depending on the voltage and
the electrolyte temperature. Different alloys will also have different effects.
Pore size is related to current density, higher volts means smaller pores.
Generally speaking, the larger the pore, the easier the dye will tak
10
Anodes and Cathodes
Supplied in each kit is a set of metal plates which can be either a cathode or an anode. The plates are called
anodes when they are used in a plating tank, and cathodes when they are used in a de-plating or
anodizing tank. Anodes are always connected to the (+) positive side of a power unit, and cathodes to the
(-) negative side.
The anodes we supply are of very pure quality. Substituting, particularly copper, is tempting but can result
in low quality copper being introduced into the bath, which can cause contamination of the solution and
disbonding of subsequent layers of plate.
Nickel Anodes 6" x 8"
Nickel anodes are supplied either singly, or in a set of 2, each with a special bandage. The bandages
should be wrapped around the anode, to make an envelope and secured with a rubber band. This
prevents the oxide that forms during plating from falling into the solution and contaminating it. The other
types of anodes do not usually require this treatment. Note how the bottom of the bandage is folded up
and then secured. Always remove the anodes from the tank after plating. Rinse and dry them to store.
Copper Anodes 4" x 8" (High Phosporous)
Supplied singly, or in a set of 2, with anode bandage. As of January 1997, we have changed our policy on anode bandages for copper,
and they will be added to each pack of anodes. Install the bandages in the same manner previously described for nickel plating. Anode
bandages in copper provide a smoother, higher quality plate. Always remove these anodes from the tank after plating. They will
deteriorate rapidly if left in the tank.
Pictured right, the anode and bandage, with a strip cut to make the tank hanger.
Chrome Anodes 12" x 12"
These larger plates are used as anodes for chrome plating. The chrome is derived from the solution and not from the anode, so these
plates are a permanent fixture. They are a specially made alloy of lead and antimony.
Chromic acid will attack the anode. forming a yellow layer of lead chromate. This acts as an insulator and prevents the anode from
functioning properly. Anodes must be removed from the tank, immediately after plating and cleaned with a Scotchbrite pad in fresh
water to remove this film. Dry and store the anode ready for the next usage.
Chrome anodes need to be affixed to a heavier wire than all other types of anode, due to the much larger current requirement of the
plating operation. To affix the anode to a thicker wire (such as jumper cables), bare approx. 2" section of the wire and roll a corner of
the anode around it. Hammer flat to secure. The anode can be hung into the tank, using the wire as its positioning support. Alternatively,
use jumper cable clips to secure the anode to the tank wall and make the connection.
PEROXIDING CHROME ANODES. As an option for chrome anodes, you may wish to treat them to prevent the build-up of ‘lead
chromate’ This yellow coating prevents the correct function of the anode. It usually occurs if the anodes are left in the solution for long
periods without regular cleaning.
Make up a solution of 15% sulfuric acid (battery acid) and 85% distilled water.
Clean the anodes with wire wool, and connect anodes to a dc power supply, one to the negative and one to the positive. Adjust the
current to obtain approx 5amps per sq foot of anode surface area. Maintain current for 15 minutes.
Reverse the polarity and repeat the process for 15 minutes.
Finally, reverse the polarity once more, and repeat the process for 15 minutes.
A dark brown coating will form on the anodes, indicating the prescence of lead peroxide.This layer will prevent the formation of the
lead chromate whilst still allowing the current to flow.
Installing the anode/cathodes
It is imperitive that you do not allow any connecting wires/clips etc. to be immersed into the plating solution. Any such foreign objects
will be dissolved by the plating action, and the result will be a contaminated electrolite.
To ensure that ONLY THE ANODE is dissolved, cut a strip down one side of the anode, about 1/4' in. Do not completely sever the strip
from the anode, stop cutting about 1/4" from the end. This strip can now be bent 180 degrees to make the hanger and contact for the
anode.
11
Drop the anode into the solution, and bend the top of the strip over the lip of the tank. You may
now use an alligator clip to attach your power line to the anode. Attach a second wire from this
anode to any other anodes.
Anode Positioning
Most items can be plated in our round tanks with an anode either side. In larger round tanks several
anodes may have to be placed around the circumference. The effectiveness of an anode
placement is something you will learn by experience, but as a general rule, try to keep the anode at
least 3" away from the article being plated and no more than 9" away. When chrome plating,
remember that chrome has poor throwing power, so anodes should be evenly placed around the
object.
For long objects, several anodes may have to be placed along the length of the tank.
Objects with recesses may not plate effectively in the recessed corners. To overcome this, you
may need to place the anode closer to the recess and actually form it to conform to the recess.
To reach difficult areas, you may need to make a cut in an anode edge and bend a strip upwards, so that it
can be pointed into the recessed area. This technique is especially useful for plating inside tubes. See the
section on HARD CHROME PLATING, for specific anode design.
In the picture, left, a long object is required to be plated on one side only. Both anodes have been placed on
one side, facing the part. Their strips are joined together ready for the positive terminal from the power
supply to be attached.
If both sides were to be plated, anodes would be placed on either side of the part, which would be centralized
in the tank.
Left. The two tanks bars have the part suspended on copper wire. If the part were to be plated on both sides,
additional anodes should be placed opposite the existing ones.
Anodes give out 'Lines of Force' similar to a magnetic field. These lines travel in almost
straight lines form the anode to the part, but, like magnetic force fields they will
bend slightly. So an object being plated which is facing only ONE anode, will
generally only the side facing the anode plated. Because the 'Lines of Force' bend,
some of the back edge of the part may also get plated. This phenomonen will vary from
part to part, also depending which type of plating you are doing. Generally, zinc plating
will almost plate all the back side of a part, whilst chrome will not, as it has poor
'throwing power'.
Here are several configurations of anode placement. Tank C shows the anodes
hung centrally in the tank, and bent around to keep their surface
equidistant from the part. This is especially useful when chrome plating a small
part. If the anodes were left in the A tank position, the distance from the part
would be so great that the 'chrome anode would be unable to 'throw' the power
across to the part, resulting in a patchy, on existant plate. The anodes in tank C
could also be made into a complete tube, with the part hung in the center.
The configuration in tank B could be used when the part has many
'nooks and crannies', ensuring the 'Lines of Force' come from many
directions.
Here left, the lines of force are shown. Note in A that the areas
directly opposite the anodes get more lines of force, so get plated
heavier. Whereas the ‘sides’ of the part get much less.
In tank D, note that the lines of force are only attracted to one side
of the object, so the side ‘in shadow’ from the anode doesn’t get plated.
GP Plates 8" x 8" ( General Purpose Plates) Used for Anodizing, Stripping.
12
In these instances the plates are called cathodes, and are wired to the negative side of the power unit. They may be attached to wire in
exactly the same way as the chrome anodes. If the tank is to be stored for any length of time, it is advisable to remove the anodes/cathodes,
wash & dry them and store them separately.
Making up the tanks
There are two basic types of tanks;
A. PLATING B. DE-PLATING.
A. PLATING TANKS are used for applying the various metals to the
objects. One type of tank will only plate one type of metal, therefore you will have
several tanks for triple chrome plating, where the requirement is to copper, nickel
then chrome plate. The metal plates used in these tanks to supply the plating metal
are wired to the positive side of the power source and are, in this instance, called
the ANODES. The part to be plated is wired to the negative side of the battery and is
called the CATHODE.
The negative CATHODE attracts metal from the positive ANODE.
B. DE-PLATING TANKS are used for:-
1. removing old plate
2. anodizing aluminum
3. dissolving rust
4. electric etching
These tanks are set up in exactly the same way as the plating tanks, except that
they are wired up IN REVERSE.
So you end up - DE-PLATING.
Our previous policy was to bolt the anodes/cathodes to the side of the tank, but
now we prefer to cut a strip along the long side of the anode and use this as the
hanger. This enables the anode to be placed deeper into the solution, with no fear
of contamination from the hanger.
Plating long objects.
As our tanks are cylindrical in shape, this can cause some problems when plating longer objects. Most
objects can be half plated, then turned in the tank and the other half plated. Where there is a join mark,
this can be buffed out leaving no signs of its existence.
Pictured right is a plastic window box. Note how the anodes are placed on one side only. In this
instance, only one side of the object needs plating. More anodes would be needed to plate both sides,
or the object could be turned and the process started over for the other side.
13
14