Here at Domepans we work with various types of metals to accomplish a full range of diversified sounds. Taking care of your instrument is fairly straight forward as metals are none porous materials, they just require a damp cloth with a bit of dish washing soap to clear natural oils off them. Using solvent based products is not recommended, especially on instruments with a design. Light rust spots can be rubbed gently with a dish washing abrasive pad.
Gongs are shellac coated and should be protected from rusting. Over time you might have to re-coat it. Use natural shellac clear finish from you hardware store.
Shellac is an amazing natural product that enhances most harmonics due to the nature of its hardness.