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Clear Trivalent Zinc Electroplating
Clear Trivalent Zinc Electroplating, also known as clear chromate, is the process of metal being coated with a protective layer, producing a shiny silver or blue hue.
Once the clear chromate process is complete, it creates a strong corrosion defense, which protects the metal from erosion. The barrier prevents moisture and other corrosive elements from reaching the underlying metal and compromising the metal’s integrity. Within outdoor or highly destructive environments, metals are subject to corrosion. Once a metal is protected with clear zinc plating, it provides low visibility of corrosion. Compared to yellow or black zinc plating, where white rust is more pronounced and visible to the naked eye, clear zinc plating creates a barrier that helps make white rust less visible.
A large benefit of clear trivalent is aesthetics. The silver appearance of the metal substrate will not be covered or distorted through the coating process, allowing the metal's original appearance to shine. This is a great option when the integrity of the metal’s appearance is crucial. This can be especially true when working with automotive parts, architectural hardware, decorative items, furniture, and consumer electronics. If the original color and texture of the metal need to be preserved and displayed, clear trivalent coating is the perfect solution.
Yellow Trivalent Zinc Electroplating
Yellow Trivalent Zinc Electroplating is also known as yellow zinc chromate or yellow passivation. Much like the process of clear trivalent zinc electroplating, this is also a chromate conversion coating. Due to the chromate being yellow, it provides the metal with a distinctive appearance producing a beautiful yellow-gold coating on metal surfaces.
Once the plating process is complete, it creates a strong corrosion resistance, which protects the metal from rust and degradation. The barrier prevents moisture and other corrosive elements from reaching the underlying metal and compromising the metal’s integrity. A large benefit of yellow zinc plating is the aesthetics of the result and the benefits that come with it. The yellow-gold color of the coating is visually appealing, making it desirable for certain applications. Due to the striking end results, yellow zinc sets the newly coated pieces apart from the rest for quick identification within the assembly line or workforce.
Trivalent Zinc plating is considered more environmentally friendly than older hexavalent chromate processes. Hexavalent chromium has a variety of negative health and environmental impacts. Here at Craft Coating, we take environmental friendliness and the safety of our staff seriously. This is why we do not provide hexavalent yellow on our production lines. The Restriction of Hazardous Substances Directive, otherwise known as RoHS, restricts the use of certain hazardous substances in electrical and electronic equipment. When plating with yellow zinc, the use of trivalent chromates helps to ensure compliance with the RoHS directive. This is also a similar case with clear trivalent zinc plating.
Black Trivalent Zinc Electroplating
Black Trivalent Zinc Electroplating provides the parts with a black or gray appearance once the coating process is complete. Though this coating is more subjective to scratches than yellow or clear coatings, black zinc provides similar corrosion protection, creating resistance from rust and degradation. The barrier prevents moisture and other corrosive elements from reaching the underlying metal and compromising the metal’s integrity.
The Restriction of Hazardous Substances Directive, otherwise known as the RoHS, restricts the use of certain hazardous substances in electrical and electronic equipment. When electroplating with black trivalent zinc, the use of trivalent chromates helps to ensure compliance with the RoHS directive. This is also a similar case with yellow zinc trivalent plating.
Hydrogen Embrittlement Relief
Hydrogen Embrittlement is a phenomenon that can occur in metals when hydrogen atoms become trapped within the metal lattice. Even if a metal has undergone zinc plating, the part can still be susceptible to this phenomenon. The trapped hydrogen greatly increases the metal’s vulnerability to cracking and overall failure. This is especially true when the parts are under tensile stress, regardless if the stress is well below the metal's typical yield strength. To mitigate hydrogen embrittlement within zinc-plated parts, hydrogen embrittlement relief (HER), also known as hydrogen embrittlement baking, is employed.
The process of HER involves subjecting zinc-plated parts to a post-plating heat treatment. The heat treatment helps to reduce the volume of hydrogen trapped within the metal and mitigates the risk of hydrogen-induced cracking and embrittlement. After the plating process is complete, Craft Coating will bake the zinc-coated parts at approximately 400 °F for four hours. There are certain specifications that require more baking time, and we are able to accommodate most requirements.
The practice of HER is especially crucial for high-strength steels and certain alloyed materials, as they tend to be more susceptible to hydrogen-induced cracking. However, not all zinc-plating parts require hydrogen embrittlement relief. Whether or not post-plating heat treatment is required is determined by factors such as the type of metal that has been plated, which plating process was selected, the specific application, and any risks associated with hydrogen embrittlement..
Craft Coating has its own shipping truck that travels within 150 miles of Oshkosh. Not only can we ship internally within Oshkosh, but our company is also highly equipped to find the correct shipping method for your order. With our connections, we can assist you by setting up common carriers or UPS shipments. Whatever your trucking needs may be, we have you covered. Give us a call, and we will be happy to assist you in finding the perfect match for your order!
Here at Craft Coating, we are an ISO 9001 facility. We are able to perform thickness testing, salt spray testing, and adhesion testing at our facilities. The most common test we carry out are as follows:
Thickness testing per ASTM B499
Passivate testing per ASTM A967
Burnishing testing per ISO 2819
Salt spray testing per ASTM B117