Gauge reads exact current density in anodizing tank
PRINCIPLE OF OPERATION
This Current Density Gage measures the current applied to an aluminum plate with an area of exactly 1 square foot. The resulting current reading is therefore a direct reading in amps per square foot. (ASF)
To use it, simply mount the unit on a bus bar along with the work to be anodized. Pressing the button on the top will display the current reading. After ramping the current ini your tank up to the target current density, set your rectifier to maintain this constant current. The digital display will shut off automatically to conserve battery power.
Other features:
- The device is powered by a 9V “square” lithium battery.
- Bright digital display is easily visible in any environment.
- Replaceable hook.
- Replaceable stainless toggle clamp.
The Current Density Gauge allows the anodizer to know precisely what the current density is in the tank for optimum anodizing quality.
After mounting the Current Density Gauge on a bus bar, the operator presses the button for a digital display of the current density. Monitoring the displayed current density (in ASF) allows the operator to set the correct constant amperage on the rectifier for the duration of the anodize cycle.
CONSTANT VOLTAGE PROBLEMS
The problem with constant voltage anodizing is that there are many variables that change the voltage: bath temperature, acid concentration, aluminum concentration, the aluminum alloy, and the voltage will change during the cycle because of the resistance of the oxide layer! So its hard to know what the correct voltage should be. If the anodizer get it wrong then problems with “mossy oxides” or inability to seal will result. In addition, as the anodic film builds, the resistance increases and the current density will decay as the anodizing process progresses. This produces an anodic oxide that is less abrasion resistant, and increases the time required to form the necessary oxide thickness.
When the surface area of part isn’t known, many anodizers make a guess at the correct voltage and maintain a constant voltage on the tank. Even if the area is known, its just faster and easier to just read the current density.
WHY ANODIZE BY CURRENT DENSITY?
With constant-current anodizing, the voltage varies over time to ensure that the part receives an unchanging amount of electrical current as the anodized film grows. This constant current provides a constant rate of film growth, which means the 720 rule can used to calculate the rate of that film growth. (in thickness per minute) With this advantage you don’t need to interrupt the process to take measurements.
Products Finishing article on constant voltage vs. constant current by Larry Chesterfield. Another article discussing constant voltage vs constant current control in Finishing and Coating.
THE 720 RULE
The 720 rule can be used to determine the time required to create a certain thickness.
Minutes to anodize = [mils (of coating desired) x 720] / ASF
So for example, if you want to build 0.001″ thickness and your current density is 15 ASF, then it will require 48 minutes. (720 x 1mil/15ASF=48mins) Online calculator here.
Or use our phone app. Link in the documents tab below. Search for “720 Rule” at the Google Play store or Apple App store and look for the red ball icon.
Settings for adjusting the display delayed OFF time
720 rule calculator App. Calculates the time required to reach required thickness, and then times the load. Available on both the Apple App store and Google Play store.
Press release in Finishing and Coating Sept. 2025
Press release in Products Finishing. Sept 2025
Press release in AAC. (link coming soon)
MATERIALS
- Enclosure material……………………………ABS
- Enclosure screws…………………………… 316 stainless steel
- Enclosure seal……………………………… solid TPU elastomer
- Pushbutton bezel…………………………… anodized aluminum
- Spline………………………………………… 6061 Aluminum
- Spline coating…………………………………Talisman thermoplastic (PP/PE) 0.025″ thickness
- Knob……………………………………………polypropylene
- Plate mounting hardware…………………… titanium (grade 5)
- Hook mounting screws……………………… 316 stainless steel
PHYSICAL PROPERTIES
- Battery………………………………………. Lithium Manganese Dioxide (Ultralife U9VL)
- Current consumption during display…………120mA
- Battery lifetime……………………………… 10 hours
- Ingress protection…………………………… IP65 (NEMA 4X)
Specifications PDF
Order Here
CURRENT DENSITY GAUGE
Includes battery and one Al plate.
[CDG]
$695
Options
REPLACEMENT ALUMINUM PLATE
6 x 12″ aluminum plate, 6061-T6 grade. Presents exactly 1
sq. foot of area for accurate measurements. Thickness is 0.050 inches. Center hole for mounting and rounded corners.
[CDG-P12] $22
REPLACEMENT ALUMINUM PLATE
4 x 18″ aluminum plate. 6061-T6 grade. 
Presents exactly 1 sq. foot of area for accurate measurements. Thickness is 0.050 inches. Center hole for mounting and rounded cornders. This plate takes up less width on the bus bar, but extends deeper in the tank. (requires 29″ below the top of bus bar)
[CDG-P18] $23