GB709101A - Improvements in methods of detecting surface defects in manufactured articles - Google Patents

Abstract

709,101. Testing for flaws in surfaces. NORTHROP AIRCRAFT, Inc. March 14, 1950 [March 26, 1949], No. 6401/50. Class 106 (2) A method of detecting surface defects in manufactured articles comprises applying to the surface of the article a dye dissolved in a penetrant solvent consisting of a volatile liquid mixed with an oil-free relatively non-volatile liquid having a higher surface tension than the volatile liquid, the excess penetrant being removed from the surface of the article and an absorbent substance applied thereto, - the absorbent thus becoming stained by taking up the dyed penetrant remaining in the flaws, the positions of which are thereby revealed. In a specific example, the penetrant comprises 50-75 per cent ethylene glycol monobutyl ether plus 50-25 per cent dibutyl phthalate saturated with a red dye. After application to the surface of the article, excess penetrant is removed by immersion in a cleaning fluid, e.g. kerosene, and the article is then dipped in a liquid " developer " comprising 25 per cent chalk and 75 per cent ethyl alcohol which upon drying forms an absorbent coating. Dye from cracks &c. bleeds into and stains this coating. A permanent record of the crack 2 may be made by applying a piece of adhesive tape 4 which upon removal takes with it the stained developer 3 from the area concerned. Examples of suitable volatile solvents are alcohol, ether, ester and ketone or halogen derivatives thereof, and examples of oil-free non- volatile liquids are benzyl alcohol, amyl, di-amyl butyl, dibutyl, ethyl, di-ethyl, methyl, dimethyl, acetate, butyrates, citrates, cinnamates, ethers, salicylates, glycolates, phthalates, maleates, sebacates, succinates, and proprionates.