Fuel System Varnish Contamination

Fuel-varnish forms as sticky polymerized deposits from degraded fuel in engines, so it builds up during storage and operation. This contamination shows unique gummy texture and dark color, distinguishing it from dry rust or oily residues because varnish resists solvents yet cracks under heat. On steel and aluminum surfaces, it adheres tightly and causes corrosion over time, while brass experiences reduced conductivity from the layer, so removal challenges include avoiding substrate damage during scraping. Laser cleaning works effectively because pulses vaporize the varnish selectively without harming metal bases.