The insulation gasket kit is a specially designed gasket package that use to prevent galvanic corrosion of flange face in a piping system when the material of connecting flanges is different. Here, in the image, you can see the complete kit of insulation gasket. Basically, it prevents direct metal to metal contact of two different flange material.
Insulation joint is used to break the current flow of an underground pipeline that is equipped with cathodic protection. To protect the underground pipeline from corrosion, cathodic protection is used. An external current is supplied to the pipeline. However, if this current flow continues when the line goes above-ground, it will damage the paint that applied to protect the above-ground pipeline. To avoid this situation, insulation joint is used. It is designed in such a way that it will break the flow of current. Here in the image, you can see the configuration of insulation joint.