Chapter 2 Flashcards
a complex phenomena that may involve one or more forms
corrosion
corrosion of metals, confined to the metal surface but sometimes along grain boundaries
chemical or electrical corrosion
is the deterioration of plastics and other nonmetals resulting in swelling, crazing, cracking, softening, and/or decomposition
physiochemical corrosion
initiated by galvanic action
corrosive action
an electrical potential can be set operating between two series of various metals
galvanic corrosion
corrosion rate of most metals is affected by __
pH
they are powerful accelerators of corrosion
oxidizing agents
____ tend to increase with rising temperature
alos thend to increased with an increase in the volume
rate of corrosion
involves gray cast iron in which the metals converted to graphite’s mixed with iron corrosion products.
graphitic corrosion
corrosion of brass alloy containing Zn in which the principal product of corrosion is metallic copper
dezincification
metabolic activity of microorganisms can either directly or indirectly cause deterioration of a metal by corrosion processes
biological corrosion
___ activity in the fluid can produce corrosive environment
biological activity
Microorganisms associated with corrosion are either
*___ - thrive in the presence of oxygen
*___ - thrive in the absence of oxygen
aerobic, anaerobic
how to combat corrosion
- change in the ___ environment
- use of an ___
- ___ protection
- ___ of corrosive metals
- use of ___ material in the design
*operating
*inhibitor
*cathodic/anodic
*substitution
*permissible
2 general classification of metals
metals and nonmetals
AISI
American Iron and Steel Institute
what is the most commonly used material for chemical process industries
ferrous metals/alloy carbon steel
this material contains one or more alloying components to improve the its chemical and corrosive resistance
low-alloy steel
increases toughness and improves low temperature properties and corrosion resistance
nickel
improves hardness/abrasion resistance, corrosion resistance to oxidation
chromium and silicon
_ provides added strength for higher temperature operation
MOLYBDENUM
contain 12-20% Chromium with controlled amount of Carbon and other alloys.
Martensic alloys
SS contain 15-30% Chromium with 0.1% or less Carbon content
Ferritic
_ SS most corrosive resistant among the 3, contain 16-26%Chromium and 6-22% nickel
Austinistic
exhibits high corrosion resistance to most alkaline
nickel
_ used extensively for equipment in caustic soda producing alkaline production
Nickel clad Steel
67% nickel and 30% copper; used in food industries
monel
77% nickel and 15% chromium
inconel
- Light and easy to fabricate
- Resists attacks by acid because of surface film
- Lower corrosion resistance than pure metal
- Metallic Mercury, heavy metals ions or chloride ions can cause rapid failure
aluminum and its alloys
Metallic Mercury, heavy metals ions or chloride ions can cause ___
rapid failure
- Relatively inexpensive
- Possesses fair mechanical strength
- Can be fabricated easily into different shapes
- Readily susceptible to oxidation
- Resistant to atmospheric, moisture, oxygen because a protective coating Of copper oxide is found on the surface.
copper and its alloys
- has low creep and fatigue resistance
- good resistance to sulphuric and phosphoric acid
lead and alloys
- physical properties similar to mild steel with the exception of its melting point (2996 deg C)
- Highly strong with with medium weight educing medium
- Corrosion resistance is superior in oxidizing and acid E
- Excellent resistant to seawater
- Resistant to nitric acid except with fuming nitric
- Resistant to ferric chloride and other hot chlorides
Tantalum
- Has excellent resistance to reducing environment
- Oxidizing agent caused accelerated attack
- Resists all chlorides except ferric and cupric
- Damaged by sulphuric acid above 70%
zirconium
include glass, stoneware, brick, cement
have low structural strength
inorganic nonmetals
limited to relatively moderate temperature and pressure such as plastics, rubber, wood, carbon
organic nonmetals
account for a large fraction of the purchased cost of equipment
fabrication expenses
