Showing papers in "Materials protection in 1971"

Effects of atmospheric pollutants on corrosion behavior of steels

Abstract: ALTHOUGH BOTH FIELD AND LABORATORY STUDIES HAVE CORRELATED STEEL CORROSION WITH ATMOSPHERIC SULFUR DIOXIDE CONCENTRATION, AND THE REACTION MECHANISM HAS BEEN SUFFICIENTLY STUDIED TO ESTABLISH A DEFINITE CAUSE--EFFECT RELATIONSHIP, UNEXPLAINED SITE-TO-SITE AND SEASON-TO-SEASON VARIATIONS HAVE LED TO THE CONCLUSION THAT UNMEASURED VARIABLES ALSO CONTRIBUTE TO STEEL CORROSION. ONE APPROACH IS TO MEASURE THE CORROSIVENESS AT EACH SITE. ANOTHER, ADOPTED IN THE PRESENT STUDY, IS TO DETERMINE THE IDENTITY OF THESE UNMEASURED VARIABLES AND THE EXTENT OF THEIR EFFECTS. THE EXPERIMENTAL DATA ARE DRAWN FROM THE CONTINUOUS AIR MONITORING PROJECT (CAMP) THAT THE PUBLIC HEALTH SERVICE HAS MAINTAINED IN EIGHT LARGE CITIES AROUND THE COUNTRY SINCE 1961. THE EXPERIMENTAL PROCEDURE AND ANALYTIC EQUATIONS ARE DESCRIBED. IT IS CONCLUDED THAT MORE THAN 90% OF THE VARIABILITY IN CORROSION BEHAVIOR OF THREE TYPES OF STEEL EXPOSED AT URBAN SITES IN THE EIGHT CITIES CAN BE ACCOUNTED FOR BY THE VARIABILITY OF CONCENTRATIONS OF TWO POLLUTANTS: SULFUR DIOXIDE INCREASES CORROSION AND OXIDANTS DECREASE IT. WHILE THE EFFECT OF THE FORMER HAS BEEN OBSERVED MANY TIMES IN THE PAST, THE EFFECT OF THE LATTER IS A NEW OBSERVATION. BECAUSE THE TWO EFFECTS ARE COUNTERACTING, THE RELATIVE RATES BY WHICH THE POLLUTANTS ARE REDUCED IN THE FUTURE WILL STRONGLY AFFECT THE CORROSION BEHAVIOR OF STEELS.

The scale meter: a new method for determining the critical ph of scaling

Abstract: A new understanding of the Saturation Index is presented which leads to the concept of a critical pH, the true pH of scaling. The critical pH is about 1.7 to 2.0 pH units higher than the pH of saturation predicted by the index. The method of determining the critical pH is described as a continuous controller which utilizes this theory. The application of the controller to cooling water systems is described for several chemical treatment programs, and controller results are given.

Dissolved hydrogen analyzer--a tool for boiler corrosion studies

Abstract: Several types of waterside corrosion can attack a boiler. In many cases, the only evidence of this corrosion before tube failure is increased hydrogen in the steam. A continuous record of this hydrogen can be obtained with dissolved hydrogen analyzers which utilize the hydrogen's high thermal conductivity to detect as little as 0.2 ppb in steam. Rate of metal loss can be calculated from the amount of hydrogen in the steam, and the pattern of hydrogen release often indicates the type of corrosion. A well planned test program includes tests for sources of hydrogen other than corrosion.

Electrochemical characteristics of six aluminum galvanic anode alloys in the sea

Abstract: THE ELECTROCHEMICAL CHARACTERISTICS OF SIX TYPES OF ALUMINUM GALVANIC ANODE ALLOYS UNDER SIMILAR SERVICE CONDITIONS IN SEA WATER ARE DISCUSSED AND ARE COMPARED WITH ZINC ANODES AND PREVIOUSLY REPORTED DATA FOR ALUMINUM ANODES. THE DATA WERE OBTAINED ON COMMERCIAL PRODUCTION ANODES. THE EXPERIMENT INCLUDED 41 ALUMINUM ANODES AND 3 ZINC CONTROL ANODES. /MPP/

Telluric current effects on buried pipelines

Abstract: DATA ON TELLURIC GRADIENTS AND ON THEIR EFFECTS ON BURIED PIPELINES ARE ANALYZED. IT IS CONCLUDED THAT WHEN PROTECTION SYSTEMS FOR COATED PIPELINES ARE DESIGNED TO THE CRITERION -0.85 V, PIPE-TO-SOIL POTENTIAL CHANGES DUE TO TELLURIC CURRENTS HAVE AN INSIGNIFICANT EFFECT ON CORROSION AND THAT THE TELLURIC CONTRIBUTION TO CORROSION OF BARE STEEL PIPELINES ALSO IS IN SIGNIFICANT. /AUTHOR/

Compatibility of impressed current cathodic protection with paint systems

Abstract: Over the past few years, zinc primers have become widely used in the marine industry. Revolutionized shipbuilding techniques have brought about automated plate by plate precoating with zinc primers during the preconstruction phase. A growing interest as well as concern has been expressed regarding the effects of impressed current cathodic protection on paint systems using zinc primers. The purpose of these tests was to establish whether or not paint systems including zinc primers are compatible with automatically controlled impressed current cathodic protection systems.

Nature and behavior of corrosion products in once through boilers

Abstract: The morphology of internal boiler tube deposits and suspended corrosion products filtered from boiler water is an important consideration to designers of high pressure once-through boilers. Examination techniques covered in this paper are the use of the electron probe, scanning electron microscope, metallographic examination, X-ray diffraction, and spectrographic analysis. Correlations between morphology data and deposit effects on pressure drop and heat transfer are included.

Corrosive effects of deicing salts on automobiles

Abstract: LONG-TERM TESTS WITH STANDARD AUTOMBOBILES WERE MADE BY THREE ORGANIZATIONS---THE AMERICAN PUBLIC WORKS ASSOCIATION, THE NATIONAL ASSOCIATION OF CORROSION ENGINEERS, AND THE SALT INSTITUTE---TO STUDY THE EFFECTS OF DEICING SALTS UNDER COMMUTER-DRIVING CONDITIONS IN U.S. AND CANADIAN CITIES THAT EXPERIENCE HARD WINTERS. TWO TESTS COVERED THREE WINTERS; THE OTHER, TWO. ALL CARS WERE DRIVEN ALL YEAR LONG. PROCEDURES AND RESULTS FROM EACH TEST ARE DESCRIBED AND DISCUSSED. TWO OF THE TESTS REPRESENT A DEPARTURE FROM PREVIOUS EXPERIMENTS IN THAT COMPLETE RELIANCE WAS PLACED ON DATA FROM ELECTRICAL RESISTANCE PROBES RATHER THAN ON WEIGHT LOSS COUPONS. THE PROBE ELEMENT IS NOT SIMILAR TO UNDERBODY AREAS IN THAT IT DOES NOT TEND TO DEVELOP HEAVY DEPOSITS OF ROAD SOILS AND CORROSION PRODUCTS; HENCE IT IS MORE RESPONSIVE TO SHORT-TERM VARIATIONS IN CONDITIONS. DIRECT CONVERSION OF ELECTRICAL RESISTANCE PROBE READINGS TO CORROSION RATE IS NOT DESIRABLE UNLESS A CAREFUL, DIRECT CORRELATION HAS BEEN ESTABLISHED WITH COUPONS OR BODY METAL CORROSION RATES. THREE MAJOR FINDINGS EMERGED FROM THE TESTS: (1) WITH CERTAIN QUALIFICATIONS, DEICING SALT INHIBITORS ARE NOT EFFECTIVE; (2) ATMOSPHERIC CORROSION RATES IN URBAN AND SUBURBAN LOCATIONS WERE NEARLY IDENTICAL; AND (3) THE EFFECTS OF DEICING SALT CAN BE APPRECIABLY REDUCED BY EXPOSURE TO UNSALTED CONDITIONS FOR A PERIOD OF EIGHT MONTHS OR LESS. THE SIGNIFICANCE OF THESE FINDINGS IS DICUSSED, AND RECOMMENDATIONS AFFECTING MAINTENANCE OPERATIONS ARE MADE.

Preventing stress corrosion failures in susceptible aluminum alloys

Abstract: THE MECHANISM OF STRESS CORROSION CRACKING, SUSCEPTIBILITY FACTORS, AND PREVENTION OF STRESS CORROSION IN HIGH- STRENGTH ALUMINUM ALLOYS ARE DISCUSSED. EMPHASIS IS PLACED ON AVOIDING FAILURE BY APPROACHES BASED ON A KNOWLEDGE OF METALLURGICAL STRUCTURE, ENVIRONMENT, AND STRESS DISTRIBUTON. /MPP/

Corrosion control of galvanically incompatible metals in sea water

Abstract: The increased complexity of the equipment being used in the ocean services often requires the galvanic combination of incompatible materials. These metal combinations are subject to a great deal of corrosion while in service. Therefore, it is essential that a reliable method of corrosion control be developed. The possible controls which were tested and evaluated in this report were the elimination of salt water from the service area, de-oxygenation of the sea water, chelation of copper ions, the use of corrosion inhibitors, and the use of protective coatings (hard anodizing). Tests of controls were performed on aluminum base alloys, monel 400, brass, stainless steel, and titanium in a closed salt water system. Of the tested controls only the de-oxygenation of the sea water and the use of corrosion inhibitors met with success. De-oxygenation was the most effective control. Corrosion inhibitors require further testing and evaluation.