Anodising Troubleshooting

Whilst there can be many reasons for not getting a perfect result; remember even the professionals get it wrong on occasions.  Below is a list of general questions that are being asked by the both Professional and DIY anodisers when discussing various anodising faults.

Below is a table with some of the potential problems that may occur during the aluminium anodising process and its subsequent colouring, together with its typical cause and potential remedy.

Troubleshooting

FaultPossible reasonRemedy
Decrease in colour strength / depthDye Bath contamination
Dye used up
Improve rinsing
Add dye &/or extend dying time
Replace bath
Colour depth change in same batchInconsistence in film thicknessIncrease air agitation
Colour Depth differencesIrregular anodising conditions Different alloysKeep anodising conditions constantDye only same alloy
Dark edgesIrregular current, leading to heavy buildup of the filmReduce current density
Increase air agitation
Patchy spotsElectrolyte carry over to dye bath; Oily
Local overheating when mechanical polishing;
Gas bubbles on anodize pores
Improve rinsing
Strip and re-anodize
Increase air agitation
Dark dye spotsUn-dissolved dye particlesBoil up & agitate dye bath
Clarify dye bath by filtration
Dull / Chalky surface (removable by wiping)Inadequate film thickness / too softReduce anodize temperature / acid concentration / time
Increase air agitation
Surface pitting & soft coatingParts too close to the cathodeIncrease tank size or place the parts further away from cathode

 some additional information

Anodising Bath Make-up

For all baths with the exception of aluminum dyebaths, fill tanks 2/3 full of water. Add the required amount of products slowly with mild agitation. Add water to the operating level and mix again.

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USE PERSONAL PROTECTIVE EQUIPMENT   The chemicals and process is CORROSIVE

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 NEVER… add water into concentrated acid as this will cause excess heat generation and spattering which will lead to serious personal injuries.

For the make-up of aluminium dye-baths, fill tanks with 1/3 of water and increase to the dyeing temperature. Add the measured amount of dyes into the water whilst stirring for at least 10 minutes. Add water to make to the final volume and continue stirring until the dye solution is fully homogeneous. Check the pH of the solution and adjust to the correct pH, if necessary.

Preparation of a new dyebath

1. A cleaned tank is filled with deionized water to about 75% of final volume and raised to dyeing temperature.

2. The required amount of dye is weighed out and dissolved in a minimum amount of hot deionized water (71°-82°C) in a separate container until a slurry is formed. This is your stock solution.

3. With agitation turned on in tank, slowley pour stock solution into tank.

4. Top off the tank to its final working solution volume with more hot deionized water and agitate for 15 minutes.

5. Using a calibrated pH meter, check the pH and adjust if necessary.

6. The dye-bath is brought to dyeing temperature, where necessary check the dye instructions of on our website temperatures are in °C.

7. Product safety We strongly recommend that the company/operator uses all Personal Protection Equipment as set out in our anodising instructions. In addition read and review where applicable the Material Safety Data Sheet for the appropriate health and safety warnings before use.