Corrosion when graphite wound gaskets come into contact with carbon steel?
Thread Content
During flange connection, graphite wound gaskets are typically used to enhance sealing. But will contact corrosion occur when graphite is in direct contact with carbon steel? In reality, it won’t happen, but why?
The best method is to apply a layer of butter before adding the gasket
The part of the gasket that comes into contact with the sealing surface is made of stainless steel
This old traditional method is not recommended, as it affects the pressure-bearing capacity of the gasket. It’s possible that the gasket will be pushed out. Many foreign safety management regulations do not allow this to be done.
This operates on a different principle from microscopic carbon chemical corrosion. In the case of microscopic corrosion, micro-cells are formed, leading to discharge and reduction reactions that take place within the metal. Here, it is the ductility and plasticity of carbon that enable the formation of a sealing layer, thereby achieving a sealing effect. I hope this makes it easier to understand
The surface of the stainless steel wound gasket has a 0.2 mm graphite coating that prevents carburization when in contact with carbon steel
What are the most common causes of failure in graphite gaskets that occur during regular production? Even in the presence of corrosion, shouldn’t graphite, as a cathode, be protected?
In fact, when graphite gaskets were introduced into industry as sealing materials, corrosion was indeed a major problem. However, later improvements were made to the flexible graphite material by adding organic and inorganic corrosion inhibitors, incorporating active metals for anodic protection, and improving the manufacturing process to reduce the electrolyte content. Thanks to these improvements, the corrosion problem has been significantly reduced. :)
When graphite comes into contact with steel, a typical galvanic cell is formed, leading to a rapid process of galvanic corrosion ? ?
1. Graphite wound gaskets are not corrosive in themselves； 2. Assume graphite is used as the anode. Based on battery principles, carbon steel is used as the negative electrode, but the conditions necessary to form a circuit are lacking.