chapter 2 continued 2 Flashcards
The _____ ion is highly corrosive to ferrous metals. _____ by depolarizing the cathode, facilitates corrosive attack: thus a _____ oxygen content increases corrosivity.
chloride
oxygen
high
______ increases corrosion rate, especially in _______ flow
velocity
turbulent
_______, which normally are present in polluted seawater, greatly accelerate the attack on steel.
Sulfides
methods of corrosion control
_____ and _____ specific corrosion-resistant materials
_______ or ______ the environment
using _____ protection
selecting and using
changing or altering
cathodic
methods of corrosion control
Using a _____ between the structural material and the environment.
Using the principle of _____ allowance or ________
barrier
corrosion allowance or over-design
corrosion resistant materials
fiber reinforced plastic
corrosion or acid resistant bricks and mortar
stainless steel
changing the environment
change relative humidity
chemical inhibitors
ducting of corrosive fumes
what principle is the most common and widespread use of corrosion control
The barrier
A reversal of the corrosion process whereby the sufficient electrons are maintained on any metal surface to prevent the metal from going into solutions can be supplied either by and externally impressed current or by sacrificial materials used as anodes.
cathodic protection
Principal advantage of altering environment
simple changes. low cost. retrofit to existing facility
disadvantage of cathodic protection
limited usefulness in damp or dry areas. Immersion required
advantage of barriers
most effective and versatile. reasonable cost
disadvantage of corrosion-resistant materials
high initial cost
