The key difference between oxidizing and reducing flame is that oxidizing flames are produced in the presence of an excessive amount of oxygen, whereas reducing flames are produced in the presence of a low level of oxygen.
We use various types of burners in different applications; for example, Bunsen burner in analytical laboratories. These burners produce different flames depending on the amount of oxygen around the burner. These flames can be categorized as oxidizing, reducing and neutral flames.
CONTENTS
1. Overview and Key Difference
2. What is Oxidizing Flame
3. What is Reducing Flame
4. Side by Side Comparison – Oxidizing vs Reducing Flame in Tabular Form
5. Summary
What is Oxidizing Flame?
Oxidizing flame is the burner flame that is produced in the presence of an excessive amount of oxygen gas. When there is an excessive amount of oxygen gas around the burner, the burner produces a shortened flame. This short flame also has a dark colour. Furthermore, the oxidizing flame tends to be hissing and roaring as well.
Figure 01: Oxygen-Rich Surrounding Forms a Short Flame
Generally, this type of flame is undesirable for welding purposes. This is because this oxidizing flame can oxidize the metal surface, as its name suggests.
What is Reducing Flame
Reducing flame is the burner flame that is produced in the presence of a low level of oxygen gas around the burner. Usually, when there is not enough oxygen around the burner, the flame becomes yellow or yellowish. This is due to the presence of carbon or carbon-containing compounds such as hydrocarbons. The carbon atoms tend to combine with the oxygen atoms and form a reducing flame. Therefore, this type of flame is also known as a carburizing flame. This is because this flame can introduce carbon into molten metal. Reducing flames are important in soldering and annealing.
Figure 02: Different Flames – Reducing Flame (leftmost) and Oxidizing Flame (rightmost)
Neutral flames, on the other hand, are also important in soldering and annealing. This type of flame is produced when there is enough oxygen gas around the burner, but the oxygen content does not exceed the limits of the requirement for oxygen. Therefore, neither oxidation or reduction occurs here. These flames appear in blue colour because there is a good balance of oxygen.
What is the Difference Between Oxidizing and Reducing Flame?
Different burners produce different flames depending on the amount of oxygen around the burner. The key difference between oxidizing and reducing flame is that oxidizing flames are produced in the presence of an excessive amount of oxygen, whereas reducing flames are produced in the presence of a low level of oxygen. Oxidizing flames can oxidize metal surfaces while reducing flames can reduce molten metal. Thus, oxidizing flames are not suitable for soldering and annealing purposes, but reducing flames are ideal for these two applications.
Moreover, a visible difference between oxidizing and reducing flame is that oxidizing flames are short and have dark colours while reducing flames are long and yellow or yellowish.
You can find more details in the below infographic of difference between oxidizing and reducing flame.
Summary – Oxidizing vs Reducing Flame
Different burners produce different flames depending on the amount of oxygen around the burner. The key difference between oxidizing and reducing flame is that oxidizing flames are produced in the presence of an excessive amount of oxygen, whereas reducing flames are produced in the presence of a low level of oxygen.
Reference:
1. “Oxidizing Flame.” Oxidizing Flame – an Overview | ScienceDirect Topics, Available here.
2. “Oxidizing and Reducing Flames.” Wikipedia, Wikimedia Foundation, 22 May 2018, Available here.
Image Courtesy:
1. “OxygenRichBlowTorchFlame” By Rnbc at the English language Wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “Bunsen burner flame types” By Arthur Jan Fijałkowski – Own work (CC BY-SA 3.0) via Commons Wikimedia