Any cheap chemical converter should work and it should leave the remaining lacquer in tact. Ask the guys at a local automotive store or get this dirt cheap stuff from amazon https://www.amazon.de/Nigrin-74032-Rostumwandler-200-ml/dp/B001B4VIIM/ref=sr_1_fkmr0_1?ie=UTF8&qid=1521152155&sr=8-1-fkmr0&keywords=nigrin+rust+conveerter
@FredyCro started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
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Any cheap chemical converter should work and it should leave the remaining lacquer in tact. Ask the guys at a local automotive store or get this dirt cheap stuff from amazon https://www.amazon.de/Nigrin-74032-Rostumwandler-200-ml/dp/B001B4VIIM/ref=sr_1_fkmr0_1?ie=UTF8&qid=1521152155&sr=8-1-fkmr0&keywords=nigrin+rust+conveerter