How to Remove Zinc Screw Thread Plating
The iron and steel of galvanized screws are coated with a thin layer of zinc. This layer is designed to protect the screw against wear and tear. However, galvanization can cause these screws to become incompatible with other types of hardware. You may, therefore, wish to remove the zinc plating in order to use your screws for certain types of projects. This can be accomplished using a corrosive bath contaning a strong acid or base.
Things You'll Need
- Concentrated Hydrochloric Acid (HCl) or Sodium Hydroxide (NaOH)
- 2 glass beakers or other corrosive-resistant vessels
- Glass ladle
- Universal indicator
- Vinegar or Milk of Magnesia
- Latex gloves
Instructions
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Mix a 20 percent solution of HCl or NaOH in a glass beaker or other corrosive-resistant vessel. For each one part of the concentrated acid or base you add, add four parts water. The corrosive bath should be deep enough that you can fully submerge your screws. Be sure to wear latex gloves throughout this process, as both substances are highly caustic and will severely burn you if they touch your skin.
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Place the zinc-plated screws in the corrosive bath using a ladle or other corrosive resistant tool (this will minimize splashing). Let the screws sit in the bath overnight, or for 12 to 15 hours.
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Remove the screws from the bath using the ladle and place them in another corrosive resistant vessel. If the zinc plating is not fully removed, place the screws back in the bath and check on them hourly.
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Add the universal indicator to the solution. If you are using HCl, the mixture will turn red. If NaOH is being used, it will turn blue or purple. Add Milk of Magnesia to the solution if you are using HCl, or vinegar if you are using NaOH. Continue adding the appropriate substance solution until the indicator turns green. This will indicate that the corrosives have been neutralized and that the mixture can be safely disposed.
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Tips & Warnings
NaOH can be found in household lye.
Do not leave your screws in the bath for longer than the recommended period as the corrosive can damage the iron or steel beneath the plating.
References
- Photo Credit zinced screws image by amlet from Fotolia.com
