Hand-tool and power-tool methods

'Chip scrape and wire brush' has been a standard phrase for the preparation of steelwork for many years. But it has long been realised that it is the least satisfactory method of surface preparation of steel prior to coating. Nevertheless when labour was cheap it was the standard applied to most maintenance situations. One problem is that the standard varies with the level of fatigue of the operators at different times throughout the working day. Power tools can help to combat this particular problem

However neither the hand-tool nor the power-tool method removes millscale - and when used on B grade steel the polishing of millscale by mechanical wire brushes can be detrimental to the performance of the coating system. On flat surfaces the use of abrasive discs and wheels is preferred to wire brushes.

As a precaution it is recommended that wherever these methods are employed a 'test-specimen' area should be prepared under supervision. Such an area can then be used as a control area for the rest of the work. The only standards available are those from the American SSPC - SP2 Manual Cleaning; SP3 Mechanical Cleaning; BS 7079 Part 11989 and ISO Standard 8501 Part 11988 St2 and St3.