GB819925A - Improvements in or relating to methods of detecting surface discontinuities in articles - Google Patents

Abstract

819,925. Detecting surface flaws. SWITZER BROS. Inc. July 9, 1957 [Aug. 14, 1956], No. 24834/56. Class 106 (2). [Also in Group XL (a)] A method of testing the surface of an article for the presence of a surface discontinuity comprises forming on the surface of the article an adherent film of a liquid penetrant containing a colouring matter susceptible to fading on exposure to ultra-violet light, exposing the surface to ultra-violet light for sufficient time to substantially destroy any colour in the penetrant on the surface, but not in that lodged in a surface discontinuity and then inspecting the surface in a light which will render contrastingly visible any colouring matter remaining in a surface discontinuity. Suitable penetrants are stated to include kerosene, mineral spirits and light fuel oils. Less suitable penetrants include benzene, toluene, xylene, methyl ethyl ketone, isophorine, butyl acetate, amyl acetate and acids such as acrylic acid. Some of these latter are soluble in water and care must be taken, if a water wash is used to remove excess penetrant before leaving the films, not to use too vigorous a wash. Suitable dyes include that sold under the Registered Trade Mark " Fluorol 5GA," perylene and celliton brilliant yellow FFA, all of which fluoresce and are soluble in the above mentioned penetrants. The mixture may be applied in any suitable way, either to leave a thin film or else to leave an excess of liquid which may be removed by wiping or hosing with water. The inspection may be made under ultra-violet light, or a developer such as french talc may be applied to the surface which is then inspected under visible light.