| 摘要 |
An aqueous liquid composition containing acid fluoride ions (i.e., HF2) not derived from hydrogen fluoride, together with an acid stronger than acid fluoride ions, and, preferably, surfactant, is very effective in brightening unpainted metal surfaces such a s those of stainless steel and aluminum without reducing the transparency of any glass objects such as windows with which the composition may come into contact. Otherwise similar compositions containing aqueous hydrofluoric acid usually etch glass in such a way as to reduce its transparency. The invention is particularly useful for brightening soiled or otherwise darkened surfaces of rail passenger cars.
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