Corrosion has always been a troublesome companion of steel. But there are ways to protect steel parts from corrosion. With electro galvanization, for example. In the following blog article, you can read about the role AMPCOLOY® plays in this.
Why is steel actually so susceptible to corrosion? Well, steel is a ferrous metal. And just like all ferrous metals, steel tends to form rust. Because as a particularly hard and pure iron material, steel essentially consists of iron and carbon. And as is well known, rust forms when iron oxidizes with oxygen and in the presence of water.
Apart from a few special sorts of steel, almost all sorts of steel are susceptible to high-temperature corrosion. High-temperature corrosion affects many materials and has a significant negative impact on the life of many components and machined parts. Wherever temperatures significantly exceed 80°C, high-temperature corrosion can occur. This can be in car exhaust systems, but also in marine diesel engines, aircraft engines, or thermal power plants. Material fatigue due to high-temperature corrosion represents a not insignificant operating risk. In addition, contact corrosion and crevice corrosion must also be considered in all steel constructions. No metal is protected against these types of corrosion.
Through the addition of certain other metals in the manufacturing process, steel, like all non-ferrous metals, forms an oxide layer on the surface that protects it from corrosion. Hot-dip galvanizing is often used as passive corrosion protection.
In this process, the steel is immersed in a bath of molten zinc to create a corrosion-resistant coating. By immersing the steel in the zinc bath, a metallurgical reaction takes place - a so-called diffusion process. In this process, the coating forms perpendicular to all surfaces. This ensures a uniform thickness across the entire part.
In the steel industry electro galvanizing of a sheet, on one or two sides, permits finding at least three specific applications. There are two types of collectors: rather small ones of around 10 kilograms are often of AMPCOLOY® 972 and conduct the electricity to the small tables through the journals. The bigger ones of around 250 kilograms are of AMPCOLOY® 972, too, but they conduct the electricity to the big tables which are often of stainless steel. These collectors are forged and drilled with cooling canals. The current can reach up to 20’000 amperes.
AMPCOLOY® high copper alloys are particularly well suited for the electro galvanization process in the steel industry. They are engineered with exceptional electrical conductivity, unique wear characteristics as well as a high strength making them the ideal material for rolls used for zinc-plating processes in the steel industry. Rolls made of AMPCOLOY® deliver a higher lifetime, quality, and performance, ultimately resulting in an overall increase in productivity and a long-term cost reduction.
Furthermore, there are journals or spindles that are situated on both ends of the rolls. They conduct the current coming from the collectors to the rolls. Most of the journals are made out of AMPCO® 18 if the rolls are made out of AMPCO alloys, too. If the roll is made out of stainless steel, the journals are made out of AMPCOLOY® 972. It is the combination between mechanical strength, electrical conductivity, and corrosion resistance that defines the choice.
Are you interested in learning more about how to increase productivity in the steel industry? Download now our technical paper «The countless benefits of aluminum bronzes in the steel industry» to get an in-depth insight!