BIZOMAT MAKEOS · Manufacturing
Anodising Plan (Time, Current, Tank Heat, Loads and Cost per Part)
How long does this anodising load take to reach thickness, can the rectifier supply it, how much heat must the tank cooling remove, and what does each part cost?
Plan of a sulfuric acid anodising job: growth rate and time to thickness by the 720 rule with your efficiency factor, build-up per surface (as the anodising time tool), current for the load against the rectifier capacity, the electrical heat the tank cooling must remove at the bath voltage, loads and line hours for the batch, energy, and cost per part from energy and line time.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Current density | A/dm² | Anodic current density (about 1.2–2 A/dm² for sulfuric acid anodising). |
| Coating thickness wanted | µm | Total coating thickness wanted. |
| Efficiency factor | % | Factor on the 720 rule for alloy and bath (100% for the rule as written; calibrate from thickness checks). |
| Area per part | dm² | Anodised area of one part. |
| Parts per load | Parts on one jig load. | |
| Parts in the batch | Parts to anodise. | |
| Rectifier capacity | A | Largest current the rectifier supplies. |
| Bath voltage at the current | V | Voltage across the bath at this current density. |
| Bath cooling capacity | kW | Heat the bath chiller or cooling coil can remove. |
| Handling time per load | min | Time to rack, rinse, seal and unload a load. |
| Electricity price | $/kWh | Electricity price. |
| Line labour and overhead rate | $/h | Labour and overhead per hour of line time. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Current density
- What it is
- The anodising current per unit of part surface in the bath, set on the rectifier for the job.
- Units and format
- Enter a number in A/dm²: amperes per square decimetre. The form accepts 0.000001 A/dm² to 10 A/dm². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5 A/dm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Growth rate rises in proportion, so time falls; current per load and bath heat rise in proportion.
- Get it right
- A/dm²: 1 A/dm² = 100 A/m².
What this means: Coating thickness wanted
- What it is
- The total anodic coating thickness to grow, as checked afterwards with a coating thickness gauge.
- Units and format
- Enter a number in µm: micrometres (µm, microns). The form accepts 0.000001 µm to 200 µm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 µm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Anodising time is directly proportional to the thickness.
- Get it right
- Total coating, not build-up: the tool takes about a third as growth outward from the original surface.
What this means: Efficiency factor
- What it is
- A correction on the 720 rule growth rate for your alloy and bath, found by comparing measured coating thickness with what the rule predicts.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 30% to 120%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Anodising time is inversely proportional to this factor.
- Get it right
- 100 % uses the rule as written; lower values lengthen the time.
What this means: Area per part
- What it is
- The surface area of one part that is wetted by the electrolyte and anodised.
- Units and format
- Enter a number in dm²: dm². The form accepts 0.000001 dm² to 10000 dm². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 dm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- 1 dm² = 100 cm²; include inside surfaces the bath reaches.
What this means: Parts per load
- What it is
- How many parts are hung on one jig or rack and anodised together in one tank load.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 100000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More parts per load raise the current needed but reduce the number of loads.
What this means: Parts in the batch
- What it is
- The total number of parts in the order to be anodised.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 100000000. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Rectifier capacity
- What it is
- The largest current the rectifier can deliver, from its rating plate, compared with the current needed for one load.
- Units and format
- Enter a number in A: amperes. The form accepts 0.000001 A to 1000000 A. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 A as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Bath voltage at the current
- What it is
- The voltage across the tank at the chosen current density, read from the rectifier during a run.
- Units and format
- Enter a number in V: volts. The form accepts 0.000001 V to 100 V. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 18 V as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Bath heat and energy use rise in direct proportion.
What this means: Bath cooling capacity
- What it is
- The heat the bath chiller or cooling coil can remove, from its rating, compared with the electrical heat put into the bath.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 10000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Handling time per load
- What it is
- Time per load spent racking, rinsing, sealing and unloading, added to the anodising time to give line hours.
- Units and format
- Enter a number in min: minutes. The form accepts 0 min to 600 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 15 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Electricity price
- What it is
- What you pay for each kilowatt-hour of electricity, from your energy bill or contract.
- Units and format
- Enter a number in $/kWh: money per kilowatt-hour. The form accepts $0/kWh to $10/kWh. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with $0.25/kWh as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Line labour and overhead rate
- What it is
- The cost of one hour of anodising line time, labour plus overhead, from your costing or finance team.
- Units and format
- Enter a number in $/h: money per hour. The form accepts $0/h to $10000/h. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with $60/h as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
Method and formulas
- 720 rule: thickness (mil) = A/ft² × minutes ÷ 720, giving growth rate (µm/min) = 25.4 × 9.290 ÷ 720 × J × efficiency (as the anodising time tool); build-up per surface ≈ thickness ÷ 3.
- Current = J × area per part × parts per load; bath heat ≈ V × I.
- Loads = batch ÷ parts per load (rounded up); hours = loads × (time + handling) ÷ 60; cost per part = (energy × price + hours × rate) ÷ batch.
- Example: 20 µm takes 40.682 min at 75 A per load, putting 1.35 kW into the bath; each part costs about 1.1182.
Limitations
- Rule of thumb for Type II sulfuric acid anodising; hard anodising and other baths differ.
- Costs exclude chemicals, dyes, sealing and waste treatment.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Plan an anodising batch
- Size the bath chiller for a bigger load
- Quote anodising per part
Who it is for
- Platers and anodisers
- Process engineers
- Estimators
What you get
- Growth rate, time and build-up
- Current against the rectifier and heat against the cooling
- Loads, hours and cost per part
Interpreting the result
- Most of the electrical power ends up as heat in the bath: the chiller often limits the load before the rectifier does.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1500–1516. Topic reference; no source tables or recommended settings are reproduced.
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · BIZOMAT original book
Coating thickness by lift-off
In Eddy-Current Inspection by the Numbers
What it covers: Measuring anodising on aluminium as lift-off, why coating thickness is not dimensional growth, calibrating with foils, a wrong zero that drove the process off target, and tolerance intervals.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Anodising Plan (Time, Current, Tank Heat, Loads and Cost per Part) calculator