What Other Metals & Metal Alloys Can Be Passivated?
Passivation, a chemical process in which the surface of a metal is coated to corrode less easily, is a widely used process to protect materials from their environment. It is used for a number of different alloys and has found a home in a range of industries. Below, we go more in-depth on the passivation of stainless steel, metals, and metal alloys!
Passivation of Stainless Steel
Stainless steel is lighter, stronger, and more durable than a number of other alloys; these properties make the material highly prized in sectors needing an extra level of durability, such as the aerospace and automotive industries. However, this doesn’t mean that stainless steel is infinitely immune to corrosion. Stainless steel contains iron, which is prone to rust when exposed to air and water. While the chromium in stainless steel forms an outer film of chromium oxide that protects the underlying iron, that layer is thin and subject to damage if the surface experiences heavy abuse. Passivation helps to strengthen and speed formation of that chromium oxide layer to make the stainless steel more durable and less prone to corrode.
Passivation of Aluminum
It is true that aluminum doesn’t rust like iron. But aluminum will corrode over time. Aluminum naturally forms a highly durable outer oxidized layer that can protect the material. However, if that outer layer of aluminum oxide is removed, is damaged, or otherwise becomes unstable, it can expose the metal inside. The most common form of this occurring is galvanic corrosion when aluminum comes into contact with other metals.
Moreover, aluminum is a highly reactive metal. Pure aluminum dissolves if exposed to water. And even if it isn’t pure aluminum, aluminum alloys can undergo a severe dulling of the exterior finish if they get wet, or even release hydrogen gas, which is flammable.
Passivation can prevent these negative outcomes. By passivating the surface of the material, a microscopically thin layer (at most, .00004” thick) is added to give the surface added protection.
Passivation of Titanium
Titanium, one of the strongest metals around, is used when exceptional strength and durability are a requirement. Titanium forms a durable oxide layer very quickly when exposed to air. However, if particles such as iron are left undisturbed, they can contaminate the surface of the material, compromising its structural integrity.
Passivation can remove those surface contaminants, which are usually left behind during the manufacturing process while leaving the protective titanium oxide layer untouched.
Nickel and Nickel Alloys
Nickel is used in many specific and recognizable industrial and consumer products, including magnets, coinage, rechargeable batteries, electric guitar strings, microphone capsules, and plating on plumbing fixtures. Nickel alloys such as permalloy, Elinvar, and invar can be used for plating.
Passivation of Inconel and Monel
Inconel and Monel are families of nickel-based alloys known for their exceptional strength and corrosion resistance properties. Inconel contains a significant amount of chromium, and it naturally forms a strong chromium oxide layer to protect the material against corrosion. Monel has high levels of nickel and copper, and as a result holds exceptionally high corrosion resistance, particularly against seawater.
However, during the manufacturing process, the surface of the material may come into contact with iron particles and other contaminants. Welding and similar processes can also distort the surface of the material. In addition, depending on the application, both Inconel and Monel may be more subject to corrosion. Passivation is recommended to strengthen the corrosion resistance properties of both Inconel and Monel after manufacturing is complete.
Passivation of Nitinol
Nitinol is a nickel-titanium alloy sought after for its unique levels of elasticity and ability to return to its original forged shape when heated. The corrosion resistance of Nitinol comes down to its surface preparation. If the surface of the material has been ground, it may be subject to corrosion, particularly depending on the conditions, it will face. By passivating the surface of Nitinol after the manufacturing process is complete, it’s more likely to withstand corrosion environments.
With over 20 years of experience and a commitment to quality standards and processes, Electro-Max, Inc. provides the best service, unsurpassed quality, and superior passivation services. EMI is NADCAP accredited, fully registered to ISO9001:2015, and complies with ASTM A380, ASTM A 967, AMS 2700, QQ-P-35, SPS-1001, PS 2026, or customer-specific standards. Contact us today to learn more about the passivation of stainless steel, metals, and metal alloys.