NEW LIGHT ON CORROSION

CORROSION COSTS AND KNOWLEDGE ARE BRIEFLY REVIEWED. RECENT RESEARCH PROJECTS SHOW THAT CHLORINE SOLUTIONS BREAK DOWN PROTECTIVE FILM IN AN UNEXPECTED WAY. THE BREAK DOWN WAS NEITHER IMMEDIATE NOR GRADUAL. DR. HOAR EXPLAINS THAT THE OXIDE FILM CONSISTS OF IRON ATOMS BOUND BY OXYGEN ATOMS INTO A TIGHT LATTICE. IF THREE OR FOUR CHLORINES HAPPEN TO CLUSTER AROUND A SINGLE IRON ATOM THEY WEAKEN THE ELECTRIC BOND BETWEEN THE IRON AND THE OXYGEN AND THE IRON IS DRAWN INTO SOLUTION. HIGHER CHLORINE CONCENTRATIONS DECREASE THE PROBABILITY THAT A NUMBER OF CHLORINE ATOMS WILL CLUSTER IN ONE SPOT. THE NATIONAL BUREAU OF STANDARDS RESEARCH HAS RECENTLY SHOWN THAT THE FILM ACTUALLY CONSISTS OF TWO LAYERS OF DIFFERENT KINDS OF IRON OXIDE, WITH THE OUTER LAYER, A CRYSTAL FORM (CALLED GAMA-IRON OXIDE), ABOUT ONE TEN- MILLIONTH OF AN INCH THICK. THE OUTER LAYER CONTAINS SOME HYDROGEN IN ADDITION TO THE IRON AND OXYGEN. THIS HYDROGEN IS REMOVED WHEN THE FILM IS EXPOSED TO CHLORINE SOLUTION AND BREAKS DOWN. IT IS HYPOTHESIZED THAT THE HYDROGEN IS A STABILIZING FACTOR IN THE FILM. DR. KRUGER EMPHASIZES, HOWEVER, THAT EXPERIMENTS SHOW ONLY THAT HYDROGEN IS PRESENT IN THE FILM, AND DOES NOT DESCRIBE HOW IT IS BOUND UP IN THE CRYSTAL LATTICE. ELECTRON DIFFRACTION STUDIES OF THE OUTER LAYER DO AGREE WITH THE HYPOTHESIS THAT THE HYDROGEN IS PRESENT.

• Supplemental Notes:
  • Vol 93, No 7, PP 164-165, 2 PHOT
• Authors:
  • Behrens, C
• Publication Date: 1968-2-17

Media Info

• Serial:
  • Science News Letter

Subject/Index Terms

• TRT Terms: Atoms; Bonds; Chlorine; Corrosion; Corrosion protection; Costs; Diffraction; Electrons; Hydrogen; Iron; Oxides; Pavement layers; Protective coatings; Stabilizers
• Old TRIS Terms: Electron diffraction
• Subject Areas: Finance; Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00216375
• Record Type: Publication
• Files: TRIS
• Created Date: Jun 10 1994 12:00AM