A steel manufacturing firm would definitely want to improve their quality of production and prevent the problems that might arise. Providing good quality products to the customers and lowering cost by being more efficient should be one of the most important corporate objectives of a steel fabrication firm. One of the most common problems faced by steel manufacturing companies is contamination of mild steel and stainless steel. It is important for a steel fabrication industry to understand about the facts related to contamination between mild steel and stainless steel. Since people realized the precision and efficiency of laser cutting in the early 1960s, industrialists are looking for ways to implement this cutting-edge technology to their respective industries. That’s why, from clinical to aerospace use, laser cutting is ruling over metal integrity without raising any questionable eyebrows in case of profit. Laser cutting is usually the first step of the process before it continues down the line to undergo metal bending, metal rolling, and other types of metal fabrication in stainless steel, mild steel and aluminium.

Contamination refers to the situation where the thin passive film on the surface of the metal is permanently damaged and that causes corrosion. It can further be simplified as iron residue on the surface of the stainless steel as cast or wrought.

There are lots of reasons related to the contamination of stainless steel, and one of the major factors is mild steel, other two common factors are carbon and salt. They are supposed to be eliminated during manufacturing and shipping so that the oxide surface layer protecting the stainless steel beneath is unaffected.

Stainless steel and mild steel:

Stainless steel is a result of steel alloy with a minimum of 11.5 wt% chromium content. Stainless steel does not corrode or rust easily as ordinary steel. They are less malleable and harder than mild steel, as well as more resistant to corrosion.  Whereas mild steel is stiff and strong. They are also magnetic, hence widely used in motors and electrical appliances. Corrosion can easily occur in mild steel and their use has to be specific determining the environmental conditions.

Contamination between mild steel and stainless steel:

When the mild steel comes in contact with the stainless steel, there is a chance of breaking the protective oxide film on the surface of steel which forms a corrosion cell that can be referred as stainless steel – mild steel interface.  There are some major causes of mild steel contamination:

1-     Unprotected transportation of stainless still in railway wagons – usually there are lots of mild steel or general iron materials present within the railway wagons, which can easily come in close contact with the newly fabricated steel, and cause contamination, which might result in rust in future.

2-     Falling particles of flame cutting and welding – during cutting or welding, particles of mild steel can easily come in contact with the stainless steel. Also, the cutting tools can be made from other types of iron or mild steel.

3-     Contamination from the grinding dust created by the use of power tools – for the use of power tools, the same rule applies. Use of power tools can cause dust of mild steel which can easily be a source of contamination in the stainless steel fabrication procedure.

4-     Basic tools that have been already used on mild steel, such as – screwdrivers, files, drills and other polishing tools. The basic tools already used on mild steel might have some small mild steel particles attached to them. Hence using the same tools for stainless steel manufacturing process can transfer the mild steel residue to the stainless steel, hence creating the possibility of rust in near future.

There can be so many other ways that can lead to mild steel and stainless steel contamination; this can cause serious problems for the quality of the stainless steel produced. Hence preventive measures should be taken in order to overcome the situations that cause the mild steel and stainless steel contamination. Careful measures during fabrication procedures can help to overcome this problem.

Effects of contamination: contamination on stainless steel certainly have lots of consequences. They can be about the appearance, material identification, application, and others

Appearance – stainless steel is supposed to be somewhat superior to corrosion, and have a shiny outlook. Formation of rust can be surely objective and the reddish or brown deposits on the surface can be easily recognized. The quality of fabrication will be questioned instantly. They are supposed to be stronger, hence people might want to avoid stainless steel that shows visual rust.

Material identification – the most common identification of stainless steel is by the shiny and rust free look. Contamination can lead to rust, and others might assume that it is iron or steel. The customers will not be satisfied and may lead to loss of reputation for a particular company.

Application – stainless steel is sometimes used in specific precision handling of pure substances, such as chemicals, cosmetics, and pharmaceuticals. Presence of iron, even in small amount, can cause problems and issues hence the particular contaminated stainless steel would be unfit for the use.

There could be certain other factors associated with the contamination of mild steel and stainless steel; it is not possible to include all the consequences, but some of the major ones are explained.

How to prevent:

The surface contamination between mild steel and stainless steel can not only negatively impact the visual appearance of the stainless steel but also can affect the performance, so it is necessary to avoid the procedures that cause this in the first place. Prevention should be the primary objective.

The fabrication industry has to follow some basic rules and take careful precautions to avoid contamination of stainless steel. Some key ways to do that is described below.

1-     Proper protection – the stainless steel should always be properly covered by plastic and other wrappings as a protective measure, so that mild steel filling and other contaminants cannot settle on the surface of the stainless steel.

2-     Separating tools – tools that have been used on mild steel can transfer their small particles to stainless steel if used on them. So it is better to avoid using the same tools on both types of steel. To prevent stainless steel contamination, it is better and easier way to use different sets of tools for different steels.

3-     Cleanliness – Highly clean area will be preferred to keep the stainless steel free of mild steel dust particles or other particles that can cause contamination. Proper use of vacuum cleaner and other cleaning tools should be utilized to maximize cleanliness.

4-     Use plastic rope – using metal cables to tie stainless steel can cause the same problem of contamination, it is better and safer to use plastic cables for the use of binding and while transportation.

Bottom line

Material contamination between mild steel and stainless steel is common. The contamination causes rust to build up and effects the looks and performance of stainless steel. Certain preventive measures can be taken to avoid this contamination problem