Showing papers in "Materials protection in 1969"

Criteria for cathodic protection of steel in concrete structures

Abstract: THOUGH CATHODIC PROTECTION OF STEEL IN CONCRETE IS NORMALLY NOT REQUIRED, ITS APPLICATION TO REINFORCED CONCRETE STRUCTURES IS SOMETIMES JUSTIFIED TO PREVENT OR ARREST CORROSION IN HIGH CHLORIDE ENVIRONMENTS. IN SUCH CASES, THE PASSIVATING EFFECT OF PORTLAND CEMENT SHOULD BE RECOGNIZED, AND, AS ILLUSTRATED BY THE EXPERIMENTS REPORTED IN THIS PAPER, THE CRITERIA FOR CATHODIC PROTECTION OF REINFORCED CONCRETE STRUCTURES ARE ENTIRELY DIFFERENT FROM THOSE FOR BARE OR ORGANICALLY COATED STEEL STRUCTURES. /MP/

Unpainted high strength low alloy steel

Abstract: PROPERTIES OF LOW ALLOY STEELS ARE DISCUSSED AND GUIDELINES ARE PRESENTED FOR THEIR USE IN BUILDINGS AND OTHER STRUCTURES. FACTORS THAT AFFECT THE ATMOSPHERIC CORROSION OF STEEL AND THE INFLUENCE THAT CERTAIN ALLOYING ELEMENTS HAVE ON IMPROVING ATMOSPHERIC CORROSION RESISTANCE OF STEEL ARE DISCUSSED. ALSO RESULTS OF AN EXAMINATION OF RUST FILMS ON EXPOSED CARBON STEEL AND CORROSION RESISTANCE LOW ALLOY STEEL AND ELECTROCHEMICAL STUDIES ON EXPOSED SAMPLES OF THESE STEELS ARE DETAILED. /AUTHOR/

Four phenomena affecting cathodic protection and corrosion rates

Abstract: THE INFLUENCE OF CATHODIC PROTECTION AND CORROSION RATE ON BURRIED STRUCTURES OF ELECTRO-OSMOSIS, COATING HOLIDAY SIZE, A-C DISCHARGE, AND UNDERFILM MOISTURE ARE OFTEN NOT FULLY UNDERSTOOD OR CONSIDERED BY CORRISION ENGINEERS. THE BACKGROUND AND SIGNIFICANCE OF THESE FOUR PHENOMENA ARE DISCUSSED. IT IS CONCLUDED THAT: (|) ELECTRO-OSMOTIC EFFECTS HAVE A DIRECT INFLUENCE ON THE OPERATION OF GROUND BEDS AND ON CERTAIN PHENOMENA AT THE PROTECTED CATHODE, (2) THE CURRENT DENSITY FOR A GIVEN DRIVING VOLTAGE VARIES INVERSLY WITH THE HOLIDAY SIZE, (3) ALTERNATING CURRENT FLOW BETWEEN A METAL AND AN ELECTROLYTE DOES RESULT IN CORRISION. THIS CAN CAUSE SEVERE CORRISION OF ALLUMINUM AT HIGH CURRENT DENSITY. FOR STEEL AND COPPER, HOWEVER, THE RATE IS OF THE ORDER OF ONLY 0.1% OF THE CORRISION THAT WOULD THEORETICALLY BE EXPECTED FROM THE SAME D-C MAGNITUDE. THIS CORROSION EFFECT ON STEEL PIPELINES IS READILY OVERCOME BY CATHODIC PROTECTION PROCEDURES. AND (4) WHILE THERE CAN BE AREAS IN CONTACT WITH MOISTURE UNDER A DISBONDED COATING THAT ARE NOT REACHED BY CATHODIC PROTECTION, THE RATE OF CORROSION AT THESE AREAS ARE, UNDER MOST CONDITIONS, INSIGNIFICANT OR SELF-LIMITING. MORE RESEACH IS NEEDED ON THE SUBJECT.

Determining a standardized procedure for evaluation of automotive rustproofing compounds

Abstract: AN INVESTIGATION WAS CONDUCTED TO FORMULATE A BASIS FOR A STANDARDIZED PROCEDURE FOR EVALUATION OF RUST-PROOOFING COMPOUNDS FOR CARS. THE TREATMENT OF INNER SECTIONS OF AUTOMOTIVE BODIES WITH ANTI-RUST COMPOUNDS IS A WELL- ESTABLISHED PROCEDURE TO DECREASE DANGEROUS INSIDE-OUT CORROSION. THE TECHNIQUE, REFERRED TO AS THE ML-METHOD HAS GAINED A WIDE ACCEPTANCE AND IS APPLIED TO USED CARS AS WELL AS NEW ONES. IN 1964, ABOUT 70 PERCENT OF ALL NEW CARS SOLD IN SWEDEN WERE TREATED ACCORDING TO THE ML-METHOD. THREE RUST-PROOFING COMPOUNDS FOR AUTOMOBILES WERE EVALUATED IN LABORATORY AND FIELD TESTS. LABORATORY EXPERIMENTS COMPRISED SALT FOG TESTS ACCORDING TO ASTM B117-64 AND IMMERSION IN SALT SOLUTION. THE THREE COMPOUNDS GAVE VERY DIFFERING RESULTS. ONE COMPOUND WHICH HAS A HIGH VISCOSITY AND A HIGH FILM WEIGHT SHOWED A GOOD PROTECTION AGAINST THE DIFFERENT CORROSIVE CONDITIONS DURING THE TEST PERIOD ON FREE SURFACES, BUT PROBABLY DUE TO LESS ABILITY TO FLOW INTO A NARROW CREVICE ON THE TEST PANEL, GAVE LESS PROTECTION IN WELDED SEAMS. THE OTHER TWO COMPOUNDS HAVE LOW VISCOSITIES AND LOW FILM WEIGHTS. THEY SHOWED LESS ABILITY TO PROTECT THE TEST PANELS AGAINST RUSTING. THE SAME COMPOUNDS WERE USED IN THE FIELD TESTS. THE COMPOUND WITH HIGH VISCOSITY AND HIGH FILM WEIGHT GAVE A GOOD PROTECTION DURING THE PERIOD OF THE TEST. THE OTHER COMPOUNDS FAILED TO PROTECT THE OUTSIDE OF THE TEST SPECIMENS SUBJECTED TO EROSION. THE LIMITED NUMBER OF COMPOUNDS TESTED DOES NOT ALLOW ANY STATEMENTS REGARDING THE CORRELATION BETWEEN THE FIELD TESTS AND THE ACCELERATED TESTS IN THE LABORATORY.

Zinc-rich coatings: characteristics, applications, and performance

Abstract: CHARACTERISTICS, ECONOMICS, AND PROCUREMENT OF ZINC-RICH COATINGS ARE DISCUSSED. THE ZINC-CHROMATE IS VERY IMPORTANT IN PREVENTING PIN-POINT RUSTING AND MILL SCALE LIFTING IN STEEL. BECAUSE OF ITS SOLUBILITY, ZINC-CHROMATE IS VERY EFFECTIVE, BUT USUALLY MUST BE INCORPORATED HAVING SOME ALKYD OR PHENOLIC RESIN. THE ZINC DUST-ZINC PAINTS ARE WIDELY USED IN WATER IMMERSION. ZINC COATINGS PROVIDE CATHODIC PROTECTION FOR STEEL SURFACES BECAUSE ZINC IS LESS MOBILE THAN STEEL ON THE ELECTRO-MOTIVE SERIES. REQUIREMENTS OF A PROPER ZINC-RICH PAINT FORMULATION INCLUDE FREEDOM FROM HYDROGEN EVOLUTION IN THE CAN, DENSE SETTLEMENT IN THE PIGMENT, AND BLISTERING IN SEA WATER. THE STEEL STRUCTURES PAINTING COUNCIL MANUAL OFFERS GUIDANCE IN THE SELECTION AND USE OF THE ZINC-CONTAINING PAINTS. ZINC IS ONE OF THE MOST USEFUL MATERIALS FOR PROTECTIVE COATINGS ON STEEL.

Research on notch plasticity may contribute to understanding of stress corrosion cracking

Abstract: RESEARCH JUST COMPLETED AT THE OHIO STATE UNIVERSITY ON FACTORS LIMITING PLASTIC STRAIN UNDER A NOTCH (OR CRACK) MAY PROVE IMPORTANT IN ELUCIDATING CERTAIN ASPECTS OF PLASTIC ZONE BEHAVIOR IN STRESS CORROSION CRACKING. IT WAS FOUND THAT THE PLASTIC ZONE AT THE TIP OF THE CRACK EXPANDS ON LOADING UNTIL A CRITICAL STRAIN AT THE NOTCH ROOT IS ATTAINED. AT THIS STRAIN, THE MATERIAL UNDERGOES A RHEOLOGICAL TRANSFORMATION INTO FLUID-LIKE FLOW (VISCO- PLASTIC), IN WHICH IT IS SUSCEPTIBLE TO LOCALIZATION OF FLOW ALONG "CHARACTERISTICS" (SLIP LINES IN FIELDS), WHICH ARE DIRECTIONS OF CRITICAL MAXIMUM SHEAR STRESS AND ALSO DIRECTION OF PURE SHEAR. PLASTIC INSTABILITIES MAY BE MOUNTED ALONG THESE DIRECTIONS. WEAK INSTABILITIES LEAD TO STABLE SLOW CRACK PROPAGATION; STRONG INSTABILITIES LEAD TO UNSTABLE FAST PROPAGATION (BRITTLE FRACTURE). AGGRESSIVE CHEMICAL ENVIRONMENTS MAY AFFECT ONE OR BOTH OF THESE NEW MATERIAL PARAMETERS WHICH HAVE BEEN DISCLOSED, NAMELY THE CRITICAL STRAIN AT WHICH FLOW IS CONCENTRATED ALONG CHARACTERISTICS AND THE NATURE OF THE INSTABILITIES (STRONG OR WEAK) THAT CAN BE GENERATED ALONG CHARACTERISTICS. PLASTIC ZONE BEHAVIOR, THUS, INVOLVES METALLURGICAL STRUCTURE, RHEOLOGY, AND FORMAL PLASTICITY THEORY. /AUTHOR/