Untreated metal sculptures are prone to oxidation, which can lead to rust and deterioration over time. To preserve their beauty and longevity, here are the most effective ways to prevent oxidation:

1. Apply Protective Coatings: Use wax, oil, or clear sealants to create a barrier against moisture and air. Beeswax and linseed oil are popular natural options.

2. Regular Cleaning: Remove dirt and debris with a soft brush or cloth. Avoid harsh chemicals that might accelerate corrosion.

3. Control Humidity: Store sculptures in dry environments or use dehumidifiers to reduce moisture exposure.

4. Use Rust Inhibitors: Commercial products like WD-40 or specialized rust inhibitors can provide temporary protection.

5. Elevate the Sculpture: Place it on a non-metallic stand to prevent ground moisture absorption.

For outdoor sculptures, consider periodic reapplication of protective coatings and inspect for early signs of rust. Combining these methods ensures your untreated metal sculptures remain pristine for years.