Spots of corrosion located on the paint surface.
Industrial fallout: deposits from chimneys of foundries and ironworks. Rail dust and road chippings. Iron particles, which mainly occur on vertical surfaces, oxidise in high humidity and then attack the paint surface.
Spark damage: ash from electricity cables on tramways and railways. Spark damage from abrasive cutting, welding or sanding operations. The hot and sometimes glowing particles of iron burn into the paint surface.
HOW TO AVOID
Immediately remove the metal particles and regularly polish and wax the surface to avoid the problem. Where cutting or welding work is being carried out, ensure that all vehicles or vehicle parts close by are fully covered to protect them.
Use any standard metal dust remover and, if necessary, finish off by polishing the surface with Glasurit 562-1602 Fine Polishing Compound. If the metal particles are deeply etched into the paint surface, sand down the affected areas with P1200, then polish with Glasurit 562-1602 Fine Polishing Compound and finish with any standard high-gloss polish.