A Note on Instruments for Measuring the Roughness and Cleanliness of Blast-Cleaned Steel

Abstract

Success in the protection of steel by paint, sprayed zinc or aluminium or combination of these materials is strongly dependent. on the initial condition of the steel surface. For structural steel the accepted method of preparation is now mechanical cleaning by blasting with grit or shot, which may be of a variety of sizes and compositions. The degree of cleanliness attained and the roughness of the blasted surface depend on the nature of the steel, the plant and abrasives used and the conditions of blasting. Results obtained in practice vary so widely that techniques for control of the quality of the blasted surfaces are highly desirable. Through the initiative of the Civil Engineering Research Association, the Paint Research Association has been making a study of the surface properties of steel prepared for painting by blast-cleaning. This work has resulted in the development of portable instruments for the on-site measurement of roughness and cleanliness of blastcleaned steel. This paper describes two instruments which have been commissioned by the Civil Engineering Research Association (C.E.R.A.) and developed by the British Scientific Instrument Research Association from laboratory instruments devised by the Paint Research Association. The prototypes will now be subject to trials in industrial conditions organised by C.E.R.A. and supervised by P.R.A.