HOW COMPONENTS FAIL-VI

ACTIONS OF ONE OR MORE TYPES OF CORROSION /UNIFORM, GALVANIC, FRETTING, CAVITATION, STRESS AND HIGH TEMPERATURE/ CAN CAUSE COMPONENTS TO FAIL IN SERVICE. KNOWLEDGE OF THE COMPLEX EFFECTS OF CORROSION IS ESSENTIAL WHEN ANALYZING SUCH PROBLEMS. CORROSION CAN BE DEFINED AS THE DETERIORATION OF A METAL BECAUSE OF AN UNDESIRED REACTION WITH ITS ENVIRONMENT. UNIFORM CORROSION, THE MOST COMMON TYPE, DEVELOPS RATHER EVENLY OVER ENTIRE EXPOSED SURFACES OF UNPROTECTED OBJECTS. IT IS CAUSED BY SIMPLE CHEMICAL ACTION. GALVANIC CORROSION DEVELOPS WHEN TWO DISSIMILAR METALS ARE ELECTRICALLY CONNECTED IN A SOLUTION THAT CONDUCTS ELECTRICITY. THE CLOSER THE METALS ARE IN THE GALVANIC SERIES, THE GREATER IS THE CORROSION OF THE ANODIC METAL. FRETTING CORROSION IS A TYPE OF SURFACE DAMAGE THAT OCCURS WHEN TWO MATERIALS RUB WHILE VIBRATING VERY SLIGHTLY AND IS A MECHANICAL-CHEMICAL PHENOMENON. WHEN TWO COMPONENTS RUB TOGETHER, ADHESIVE FORCES CAUSE SMALL PARTICLES OF THE SURFACES TO WELD. WITH CONTINUED SLIGHT MOTION, THE WELDED PARTICLES TEAR AWAY FROM THE OPPOSING SURFACES AND REACT CHEMICALLY WITH THE ATMOSPHERE, FORMING DEBRIS OR POWER IN THE JOINT. CAVITATION CORROSION IS CAUSED BY IMPLOSION OF CAVITIES IN A LIQUID AGAINST A METAL AND IS ESSENTIALLY PITTING FATIGUE ACCELERATED BY CORROSION. VIBRATING MOTION BETWEEN A SURFACE AND A LIQUID IS SUCH THAT REPEATED LOADS ARE APPLIED TO THE SURFACE CAUSING VERY HIGH STRESSES WHEN THESE BUBBLES FORM AND COLLAPSE REGULARLY. STRESS CORROSION AND CORROSION FATIGUE ARE SOMEWHAT SIMILAR. THE FORMER INVOLVES CORROSION WITH STATIC TENSILE STRESSES, WHILE THE LATTER IS CONCERNED WITH DYNAMIC TENSILE STRESSES. HIGH TEMPERATURE CORROSION OCCURS BECAUSE ELEVATED TEMPERATURES SPEED CHEMICAL REACTIONS. PROTECTIVE MEANS AND TECHNIQUES ARE GIVEN FOR THESE VARIOUS TYPES OF CORROSION ABOVE.

• Supplemental Notes:
  • Vol 89, No 4, PP 94-97, 4 FIG
• Corporate Authors:

  Metal Progress

  ,    
• Authors:
  • Wulpi, D J
• Publication Date: 1966-4

Subject/Index Terms

• TRT Terms: Cavitation (Mechanics); Corrosion; Corrosion protection; Galvanic corrosion; Metals; Stresses; Stripping (Pavements); Temperature
• Uncontrolled Terms: Causes; Corrosive environments
• Old TRIS Terms: Fretting; Types
• Subject Areas: Geotechnology; Highways; Materials;

Filing Info

• Accession Number: 00216111
• Record Type: Publication
• Files: TRIS
• Created Date: Jun 5 1994 12:00AM