Subject to rapid rusting if wetted and exposed to air. In the event of steel products being totally immersed in water, arrangements should be made, if practicable, to allow them to remain under water until they can have immediate treatment when recovered. If they are treated immediately after immersion with one of the many dewatering oils or drying fluids on the market, rusting, which would normally arise out of the immersion, can be avoided. In the case of rust having developed before treatment is possible, this should be removed and the articles protected from further rusting by the application of a rust remover and neutralizer.
Steel products usually have a thin coating of oil or grease on them after manufacture, to prevent rusting. Steels which have the oil removed by exposure or other means may rust and they may also contain mill scale during manufacture. The customary procedure before finishing such steels is to degrease them. After degreasing, if there is rust or mill scale present, it is necessary either to pickle it or to clean it by sand or shot blasting. There are two main pickling processes:
(1) Sulphuric acid, which usually contains an inhibitor which assists in removing the rust without the steel being greatly attacked. This type of pickle is used hot.
(2) Hydrochloric acid (spirits of salt) is also used, and this is used cold.
After pickling the steel becomes very prone to rusting, and it must either be re-oiled immediately before fabrication, or, if pickling has been carried out after fabrication, it must be immediately finished.
The finishing processes are very great in number, the simplest being to give the steel a prime paint coat and finish with final coats of paint, lacquers or enamels at some later stage.
Another process is to treat the freshly pickled steel with a rust proofing product, which requires hot immersion or spray treatment with patented chemicals and produces a zinc phosphate or similar type of coating. See also under individual product headings.
- Commodity Name:
IRON AND STEEL PRODUCTS