Let’s take a closer look at cubic zirconia, rhodium, chromoly, and whether they rust.
Cubic zirconia
This synthetic gemstone rivals the beauty of diamonds. It is made from melting zirconium oxide powder and stabilizers like magnesium and calcium.
Then crystals will start to form and stabilize upon removal from heat. The cubic zirconia crystals are then cut and polished. The resulting pieces sparkle like diamonds but usually have more “colors” than the natural gem.
Notice how there is no iron whatsoever introduced in making cubic zirconia. Thus, the crystal itself does not rust. If you’re thinking about jewelry, the metal that holds the cubic zirconia may. It depends on what type it is.
Image source: Essilux
Rhodium
Rhodium is commonly used for plating material, giving a protective coat that shields the underlying material from scratches. It shares that feature with chrome. Like how wide belt sanders can give wood a beautiful finish, rhodium plating gives jewelry a strong shine. It reflects up to 80% of light and smoothens chips and scratches.
This noble metal is one of the most expensive ones, with its pure form being even more costly than gold. It is silvery-white. It’s also hard and chemically inert transition metal. It is highly corrosion-resistant and doesn’t rust.
These great properties are used as an alloying agent to form furnace coils, electrodes, laboratory apparatus, etc. It has a high melting point and is brittle, so it is widely used as an alloying agent and electroplating material.
Although the metal itself is corrosion-resistant, it can wear off over time. That is if the rhodium coating on the material is thin. If the underlying material contains iron, the jewelry or equipment will rust.
Before and after pictures of rhodium plating on jewelry
Image source: Mark Lloyd Jewellery
Chromoly
Chromoly will rust since it is an iron alloy but not as readily as other steel alloys containing iron. Two of its major alloying elements are chromium and molybdenum. It is why it is named “Chromoly.” These contribute to the corrosion resistance of Chromoly steel, increasing its hardness and melting point.
To protect this alloy steel, it is treated with coatings. You’ll mostly find this in bicycle tubing or frame because it is more lightweight than other steel frames. Its high melting point can be used in making furnace equipment, such as waste oil heaters.
Chromoly bike frame
Image source: Sprocket Store
Sheet metal
Sheet metal is metal processed into thin, flat pieces below 6mm. Depending on the material, these can be easily cut by engine-driven welders. It makes it may involve shearing and punching. It will also involve cutting and folding steel, among many other processes.
Regular steel is an alloy of carbon and iron, which will readily rust. With that being said, ones that do not rust are commonly made up of galvanized or stainless steel. Both have corrosion and rust-resistant properties. One example is stainless steel in car parts, such as idle air control valves.
In contrast, galvanized steel is commonly used for roofing materials. Galvanized steel is made by coating regular steel or iron with a protective zinc coating. It’s done to shield the underlying steel from oxidation and corrosion. Once this layer is degraded, the steel underneath will degrade.
Image source: Thomas
Galvalume
Most people confuse galvanized steel with Galvalume. Both are coatings applied to metals to protect them from corrosion and oxidation, but these two are different things.
Galvalume is an alloy invented and introduced by Bethlehem Steel in the market in 1972. This alloy coating contains zinc, aluminum, and silicon. The combination of zinc and aluminum enhances its corrosion and heat resistance.
The properties of Galvalume are described in the table below.
| Composition | 55% aluminum, 43.4% zinc, 1.6% sillicon. |
| Formability | Similar to the galvanized steel. |
| Thermal reflectivity | High due to the aluminum content. |
| Usage | Appliances and in the automotive industry. |
Galvalume is widely used in roofing materials, and it lasts longer than galvanized options. It is made by hot-dipping the carbon steel base sheet with aluminum and zinc alloy. It’s done until it reaches the right percentage of alloys.
Unpainted Galvalume roof
