A solid electrolytic capacitor comprising: a capacitor element that contains a sintered porous anode body, a dielectric that overlies the anode body, and a solid electrolyte that overlies the dielectric; an anode lead extending from a surface of the capacitor element; an anode termination that is in electrical connection with the anode lead; a cathode termination that is in electrical connection with the solid electrolyte; a casing material that encapsulates the capacitor element and anode lead; and an interfacial coating that is disposed on at least a portion of the anode termination and/or cathode termination and is in contact with the casing material; wherein the coating comprises a hydrophobic resinous material; characterised in that the adhesion strength of the coated portion of the anode termination and/or the cathode termination to the casing material is about 5 newtons per square millimeter or more as determined at a temperature of about 23°C and relative humidity of about 30%; wherein the hydrophobic resinous material contains a fluoropolymer, wherein the fluoropolymer is formed from a fluoroalkyl-substituted ethylenically unsaturated monomer, or wherein the fluoropolymer is formed from a fluoroalkyl (meth)acrylate; wherein the solid electrolyte includes an extrinsically conductive polymer having repeating units of the following formula: wherein, R 7 is a linear or branched, C 1 to C 18 alkyl radical, C 5 to C 12 cycloalkyl radical, C 6 to C 14 aryl radical, C 7 to C 18 aralkyl radical, or a combination thereof, and q is an integer from 0 to 8; and wherein the solid electrolyte also contains a polymeric counterion. a capacitor element that contains a sintered porous anode body, a dielectric that overlies the anode body, and a solid electrolyte that overlies the dielectric; an anode lead extending from a surface of the capacitor element; an anode termination that is in electrical connection with the anode lead; a cathode termination that is in electrical connection with the solid electrolyte; a casing material that encapsulates the capacitor element and anode lead; and an interfacial coating that is disposed on at least a portion of the anode termination and/or cathode termination and is in contact with the casing material; wherein the coating comprises a hydrophobic resinous material; an interfacial coating that is disposed on at least a portion of the anode termination and/or cathode termination and is in contact with the casing material; wherein the coating comprises a hydrophobic resinous material; characterised in that the adhesion strength of the coated portion of the anode termination and/or the cathode termination to the casing material is about 5 newtons per square millimeter or more as determined at a temperature of about 23°C and relative humidity of about 30%; wherein the hydrophobic resinous material contains a fluoropolymer, wherein the fluoropolymer is formed from a fluoroalkyl-substituted ethylenically unsaturated monomer, or wherein the fluoropolymer is formed from a fluoroalkyl (meth)acrylate; wherein the solid electrolyte includes an extrinsically conductive polymer having repeating units of the following formula: wherein, R 7 is a linear or branched, C 1 to C 18 alkyl radical, C 5 to C 12 cycloalkyl radical, C 6 to C 14 aryl radical, C 7 to C 18 aralkyl radical, or a combination thereof, and q is an integer from 0 to 8; and wherein the solid electrolyte also contains a polymeric counterion. R 7 is a linear or branched, C 1 to C 18 alkyl radical, C 5 to C 12 cycloalkyl radical, C 6 to C 14 aryl radical, C 7 to C 18 aralkyl radical, or a combination thereof, and q is an integer from 0 to 8; and wherein the solid electrolyte also contains a polymeric counterion.