MEASUREMENT OF PAINT FILM THICKNESS ON STRUCTURAL STEEL

THIS PROJECT WAS UNDERTAKEN TO DETERMINE THE MOST EFFECTIVE DEVICES AND PROCEDURES FOR MEASURING THE DRY FILM THICKNESS OF PAINT ON STRUCTURAL STEEL SURFACES. A STATE-OF- THE-ART SURVEY, REPORTED SEPARATELY, IDENTIFIED CERTAIN MAGNETIC GAGES AND WET FILM THICKNESS GAGES AS THE MOST PROMISING CURRENT INSTRUMENTS FOR THESE FILMS AND SUBSTRATES. AN EXPERIMENTAL SEARCH RESULTED IN THE DEVELOPMENT OF MICROSCOPY AND OTHER TECHNIQUES, WHICH COULD BE USED EFFECTIVELY AS REFERENCE CRITERIA FOR EVALUATING INSTRUMENTAL THICKNESS MEASUREMENTS. BASED ON THESE REFERENCE CRITERIA, IT WAS POSSIBLE TO SHOW THE RIGHT AND WRONG TECHNIQUES AND PROCEDURES TO BE USED IN THE MEASUREMENT OF PAINT FILM THICKNESS WITH SUCH COMMONLY USED MAGNETIC GAGES AS THE ELCOMETER, THE MIKROTEST, THE INSPECTOR, THE G. E. TYPE B GAGE, OR THE MINITECTOR. THESE FINDINGS ARE SUFFICIENTLY DETAILED TO PERMIT THE ESTABLISHMENT OF AN SSPC SPECIFICATION FOR THE MEASUREMENT OF PAINT THICKNESS ON STRUCTURAL STEEL. THE ACCURACY AND PRECISION OF MEASUREMENTS ON EACH TYPE OF INSTRUMENT WERE EVALUATED BY A ROUND ROBIN OF OPERATORS IN SIX SEPARATE LABORATORIES. AN APPRAISAL WAS ALSO MADE OF SUCH ENVIRONMENTAL EFFECTS AS LAYERS OF MILL SCALE, PROXIMITY TO EDGES, STEEL THICKNESS, TEMPERATURE, STRAY FIELDS, AND TILT OF INSTRUMENT HEAD. THE PROCEDURES ARE BASED UPON A THOROUGH ANALYSIS OF BOTH THE THEORETICAL OPERATION OF THE INSTRUMENT AND THE EMPIRICAL RESULTS OF THE ROUND ROBIN. THESE FINDINGS SHOW THAT SOME OF THE PROCEDURES IN COMMON USE DO LEAD TO SERIOUS ERRORS IN MEASURING PAINT THICKNESS AT EACH IMPORTANT STAGE: IN SETTING STANDARD SPECIFICATION REQUIREMENTS FOR NEW PRODUCTS; IN DETERMINING AND ENFORCING PRIMER THICKNESS REQUIREMENTS OVER BARE STEEL IN THE FABRICATING SHOP; IN DETERMINING THICKNESSES OF INTERMEDIATE AND FINISH COATS IN FIELD PAINTING BY CONTRACTORS; AND IN MAINTENANCE PAINTING. EQUALLY IMPORTANT ARE SOME OF THE BY- PRODUCTS OF THIS STUDY. BY THE USE OF THE SPECIAL VARIATIONS OF THE SCANNING ELECTRON MICROSCOPE, IT IS POSSIBLE FOR THE FIRST TIME TO VIEW REALISTICALLY WIDE VARIATIONS IN SURFACE HOLES, CAVES, LAYERS, AND FRACTURES IN BLAST CLEANED SURFACES, WHICH CAN BE EXPECTED TO AFFECT THE PROBLEM OF PROTECTING THESE SURFACES FROM CORROSION WITH COATINGS. "LOSSES" OF PAINT IN SURFACE VALLEYS CAN BE MORE READILY ESTIMATED. A PROMISING METHOD HAS BEEN INDICATED FOR ESTIMATING DRY FILM THICKNESS SHORTLY AFTER APPLICATION OF WET PAINT. /AUTHOR/

• Corporate Authors:

  Pennsylvania Department of Transportation

  1215 Transportation and Safety Building
  Harrisburg, PA  United States  17120

  Steel Structures Painting Council

  4400 Fifth Avenue
  Pittsburgh, PA  United States  15213

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Keane, J D
  • Shoemaker, T L
• Publication Date: 0

Subject/Index Terms

• TRT Terms: Corrosion protection; Measurement; Measuring instruments; Microscopy; Paint; Steel; Thickness
• Old TRIS Terms: Steel protection
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00215977
• Record Type: Publication
• Source Agency: Federal Highway Administration
• Report/Paper Numbers: Study No 68-39
• Files: TRIS, USDOT, STATEDOT
• Created Date: Mar 27 1972 12:00AM