Galvanized iron is iron which has been coated in a layer of zinc to help the metal resist corrosion. Steel can also be galvanized. When metal is going to be used in an environment where corrosion is likely, it is often galvanized so that it will be able to withstand the conditions. Even with galvanization, however, corrosion will eventually start to occur, especially if conditions are acidic.
There are two primary techniques which can be used to make galvanized iron. The most common is hot-dip galvanization, in which the iron is moved through an extremely hot bath of molten zinc, which may be mixed with small amounts of lead, depending on the circumstances. When the iron emerges from the bath, the zinc will have bonded, creating a layer of zinc on the surface of the iron. Sometimes, the metal may be passed through a mill to flatten and even out the coating. Another technique which can be used is electrodeposition, also known as electroplating, although this is rare.Once galvanized, iron is covered in a layer of zinc which may be shiny to dull gray. The zinc can be painted, if desired, or left plain. Painting is often done when the iron must match other building materials, or when people want to make it less obvious. In the garden, for example, it may be painted green so that it will blend in with foliage instead of standing out.
As long as the zinc coating remains intact, the galvanized iron should remain in relatively good condition. However, acidic conditions can erode the zinc over time, creating patches where corrosion can occur. Corrosion can also occur when the coating is penetrated, as when someone drives a nail through a sheet of galvanized iron, exposing the iron inside to the elements. Once corrosion starts, it can spread under the zinc, eventually causing the metal to fail.There are a wide range of uses for this type of iron, which comes in pipes, stakes, sheeting, and wire, among other formats. Many hardware and home supplies carry galvanized iron products and may be willing to cut pieces to custom sizes by request. People can also be referred to professionals who will weld or cut galvanized iron to meet the needs of a particular project.
Mild steel is the least expensive of all steel and the most common steel used. Used in nearly every type of product created from steel, it is weldable, very hard and, although it easily rusts, very durable. Containing a maximum of 0.29% carbon, this type of steel is able to be magnetized and used in almost any project that requires a vast amount of metal.Its structural strength prevents it from being used to create load-bearing girders and structural beams.Many of the everyday objects that are created of steel are made using mild steel, including automobile chassis, motorcycle frames, and most cookware. Due to its poor corrosion-resistance, it must be painted or otherwise protected and sealed in order to prevent rust from damaging it. A light coat of oil or grease is able to seal this steel and aid in rust control.
Unlike high-carbon steel, mild steel is easily welded. The properties of the steel allow the electrical current to travel through the metal without distorting the makeup of the material. Some types of high-carbon steel, such as stainless steel, require special techniques in order to properly weld the material. Being less brittle than high-carbon steels, the mild variant is able to flex and give in construction projects where a higher-carbon version could simply break.
Most of the pipeline in the world is created using mild steel. This allows the pipe to not only be easily welded into place, but also lets the pipeline flex and avoid cracking and breaking under pressure. The corrosive properties of the steel pipeline mean that it must be properly sealed through painting or a process often used on pipelines that involves wrapping the pipe with a corrosive-resistant material.Often in very cold climates, a warming type of insulating material is wrapped around the pipeline. This material helps keep the cold inside the pipe running smoothly. The wrap also prevents the soft mild pipe steel from becoming brittle and cracking. The constant expansion and shrinkage due to cold and warmth cycling in the pipe could create structural integrity problems, but these are held in check by the insulating wrap. On a much smaller scale, household pipes can be prevented from becoming cold and breaking by the use of electrical heating tape.
Mild steel pipe( seamless steel pipe, welded steel pipe)
GI pipe(galvanized steel pipe)