What is Cladding?
Cladding refers to a process where a metal, corrosion resistant alloy or composite (the cladding material ) is bonded electrically, mechanically or through some other high pressure and temperature process onto another dissimilar metal (the substrate) to enhance its durability, strength or appearance. The majority of clad products made today uses carbon steel as the substrate and aluminum, nickel, nickel alloys, copper, copper alloys and stainless steel as the clad materials to be bonded. Typically, the purpose of the clad is to protect the underlying steel substrate from the environment it resides in. Cladded steel plate, sheet, pipe, and other tubular products are often used in highly corrosive or stressful environments where other coating methods cannot prevail.
It is the final use environment that often determines the clad materials to be combined, the thickness and number of layers applied, and the temperature and time of bonding required to achieve the necessary bond strength requisite for the cladded product to be successful. Clad can be applied to the inside, outside or both sides of a substrate depending upon which surface(s) needs to be protected. Only certain cladding processes can be used to clad the inside of some substrates depending on surface geometry.
Cladded metal can be produced by many methods including explosion bonding, roll bonding, diffusion bonding, mechanical bonding, forging, laser, welding, friction welding or co-axial extrusion. The resultant clad products have either a mechanical or metallurgical bond to their substrate. Increase in thermal and kinetic energy increases chances of metallurgical bonding. The strength of the bond as well as the strength retention of the backing steel substrate determines the usefulness of the layered composites in subsequent metal forming processes or end user environments.
The common denominator of these clad production methods is that they are slow and expensive. Buyers need to weigh the advantages of cladded steel over other corrosion materials and faster production processes (from other inorganic metal finishing processes like fusion bond (FBE) epoxies, galvanizing and chromate and zinc priming) in their purchasing decisions. The current cost of clad steel limits its use in a variety of applications and industries, as the cost of clad steel for high corrosion application is about five times the cost of carbon steel.
Who Buys Cladded Product?
The primary buyers of cladded steel products today are the petroleum (oil, gas, and petrochemical), chemical, marine exploration, mining, shipping, desalination and nuclear industries. Other sectors, like infrastructure, building, pulp and paper, and food processing, also use cladded product, but to a lesser degree. Each of these industries has companies that work in extreme environments. As oil and gas companies move farther away from shore to extract crude oil, they have to deal with increasingly corrosive environments. A large number of deep-water drilling and extraction projects are already underway and many more in the pipeline are increasing the demand today growth for clad product.