There are many ways to prevent metal alloys from succumbing to corrosion or oxidation while in use. Their chemical composition can be altered to increase the concentration of anti-corrosive elements, such as molybdenum (Mo), for instance. Yet, this is often unsuitable as changing the elemental composition of the product would yield chemical/mechanical changes that could alter workability, inhibit performance, reduce tolerances, and so on.
In products like wiring, where dimensional tolerances are already incredibly fine, the preferred method of increasing corrosion resistance is coating, or surface treatment. One of the leading solutions in this instance is wire galvanization. Sometimes referred to as hot-dipping, wire galvanizing refers to the process where metal wires with a protective layer of the non-ferrous metal zinc (Zn).
Zinc is a mid-strength non-ferrous metal with a very low melting point of 420°C (788°F) and high workability. As with all non-ferrous metals, zinc has no iron (Fe) content, which means it is practically impervious to oxidation and has extremely high corrosion resistance. This makes it ideal for applying protective coatings to ferrous alloys like steel. There are many methods used to galvanize alloys, the leading one being hot-dip galvanizing.
Hot-dip galvanization involves the submersion of workpieces in a bath of molten zinc. Products with long continuous cross-sections, like wires, are galvanized by drawing them through the molten bath on wire guides. They are subsequently wiped before the zinc coating sets to ensure ideal coating uniformity.
There are many points of contact between key components in a galvanizing bath and the molten zinc, which can lead to rapid degradation and ultimately poor service lives. Though zinc has the lowest melting point of all non-ferrous metals, hot-dip galvanization demands high-performance materials to meet component lifetime objectives.
Silicon carbide (SiC) is an advanced technical ceramic that has been exploited by engineers for decades. One of the first fine ceramics used in mass industrial processes, it remains one of the leading solutions for challenging working environments associated with high chemical, mechanical, and thermal demands.
Heater tubes in non-ferrous metal hot-dip baths, for instance, are routinely fabricated using silicon carbide due to the ceramic’s exceptional thermodynamic stability and chemical integrity. Cryston® Max immersion heaters from Saint-Gobain High-Performance Ceramics & Refractories are engineered for greater lifetime expectancies, reducing ongoing maintenance requirements to ultimately increase production output.
At Saint-Gobain, we have leveraged our unprecedented experience in advanced metallurgy and technical ceramics to implement unique silicon carbide solutions throughout continuous hot-dip processes. Our cast Refrax® wire guides and sinker stones supplement high-performance ceramic heaters to increase throughput and ensure greater productivity over time. With exceptional resistance to molten non-ferrous metals, our silicon carbide solutions are also available as acid sliders, beams, and combs which can significantly increase the output of wire galvanizing baths.