My money would be on be on some sort of tannic complex with the iron/rust - de-rusters often have 'tannic acids' in their formulas. There is no worse feeling than seeing the orange, rough surface on your car that was once graced by a coat of paint.

Chloride ions are brilliant at initiating corrosion; ask the Scots, who's cars rust like crazy because of all the salt they use in winter. Evapo-Rust® safely and easily removes rust without the need for scrubbing or sanding, saving you time and effort. However, rather than go through the costly inconvenience of replacing the panel, Evapo-Rust can provide you with the solution. Lead times are shown on the product and trolley pages and are always advertised in working days (Monday to Friday). Get 5 litres [or more] set up bath, immerse components and relax with a coffee, works quickly [but I tend to leave over night].Credit subject to status, UK residents only, Toolstation Ltd, acts as a broker and offers finance from a restricted range of finance providers, PayPal Credit is a trading name of PayPal UK Ltd, Whittaker House, Whittaker Avenue, Richmond-Upon-Thames, Surrey, United Kingdom, TW9 1EH. The instructions suggest just 10 minutes is required and although that proved sufficient to get the surface rust off the offcut of sheet metal, the other items needed a longer soak. Over a period of a week or so I have de-rusted a wide variety of my tools, some dating back decades and the results have extremely good.

New: A brand-new, unused, unopened and undamaged item in original retail packaging (where packaging . I also found a box of citric - so mixed some up in jam jar for a test, leaving half to compare against.

The citric powder I've only used to clean limescale out of water boiler type things, handy to know it does rust as well. Most of them are relatively innocuous but you do need to take care removing the chemicals afterwards, while many of them can leave unsightly stains behind on paintwork. I don't mean spraying down with wd40 etc that is not ideal when storing tools in pouches or tool boxes. They mention that it does a great job on removing a lot of the rusted components, allowing them to be recovered and reused.