The Generally, intumescent coating contains active ingredients bound

The protection of metallic materials against fire has become a very important issue in the construction, petrochemical industries, marine and military fields. In case of fire such materials distort leading to the collapse of building structures and as a consequence lead to dramatic human and economic losses. Structural steel loses a significant part of its load-carrying ability when the temperature exceeds 500°C1-2. Prevention of structural collapse of a building is paramount to ensure safe evacuation of people from a building and is a prime requirement for building regulations in United Kingdom, USA and Europe2. In conjunction with that, fire retardant coatings are widely used as it is very important to protect flammability of different structures. The use of intumescent coatings is one of the easiest, oldest and most efficient ways to protect a substrate against fire. Indeed, it presents several advantages including, it does not modify the intrinsic properties of the material e.g., the mechanical properties3. involves the formation on heating of a swollen multicellular thermally stable char insulating the underlying material from the flame action4. Under the action of heat, intumescent fire retardant coatings expands and forms a thick porous charred layer which acts as a thermal barrier that protects and insulate the substrate, thereby maintaining the structural integrity of the structures. The substrate will be protected against high temperature rise and exposure to oxygen for a period of time3-4. Generally, intumescent coating contains active ingredients bound together by a binder such as epoxy. The active ingredients are, a carbon source which can be a carbon-rich polyhydric compound, such as starch, glucose, pentaerythritol (monomer, dimmer or trimer), acid source, a dehydrating agent capable of promoting the formation of a carbonaceous char from the carbon source. This is usually a source of phosphoric acid, such as ammonium phosphate, diammonium phosphate and the other phosphates. Finally a gas source, an intumescing agent that would expand the film of coating upon heating, this is usually a nitrogen or halogen-releasing compound such as urea, melamine and melamine phosphates or chlorinated paraffins3-6. Ideal compatibility between these three basic components is essential to produce an excellent fire retardancy that is, dehydration to char and release of gas in a transitional semi-liquid state sufficient to enable foaming and expansion to occur, followed by full carbonization without char collapse. Sodium borate is used as a flame retardant and smoke suppressant for wide range of plastics, rubbers, paper and textiles. It can replace antimony oxide as a synergist in plastics and rubber to enhance the activity of primary flame retardants by stepwise releasing the radicals in a wide variety of end-use products. In this study it is used as an additive. The objective of this research work is to investigate the char morphology and bonding mechanism of expandable graphite based intumescent coating using FESEM with sodium borate as an additive and zircon as char expansion agent.