Anodizing is the process of coating an alloy with an oxide layer to render its surface more resistant to corrosion and abrasion and to enhance its appearance. Further, if the alloy is to be painted in the future, anodizing offers the benefit of improving adhesion between the alloy's surface and the paint, thus rendering the paint less susceptible to weathering or chipping. However, when metallic objects acquire defective anodized layers--for instance, due to variations in anodizing conditions, scratching of anodized layers or the object's own physical abnormalities--it may be necessary to deanodize the object by removing the metal oxide coating.
- Stainless steel stripping tank
- Deionized water
- Gas-firing apparatus
- Nitric acid (70 wt percent), 150 pounds
- Oxalic acid, 100 pounds
- Laboratory gloves with a high degree of chemical resistance
- Laboratory coat
- Laboratory goggles
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Instructions
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1
Wear chemical-resistant laboratory gloves, a laboratory coat and lab goggles throughout the process to protect your skin and eyes from noxious chemicals. Prepare the stripping solution bath in a stainless steel stripping tank. Add deionized water to the tank and heat, by gas firing, from about 140 degrees F to 160 degrees F.
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2
Add nitric acid and oxalic acid to the tank. Adjust the amount of deionized water so that the total solution volume is around 380 gallons. The solution should be clear enough that you can see through several feet of it.
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3
Add alloy to be deanodized. Within fifteen minutes the alloy should be clear of the deanodized layer. Remove it from the stripping bath and rinse with deionized water.