Corrosion Ch01 Flashcards
State the definition of PH
The negative of the base 10 logarithm of the hydrogen ion concentration of a solution given in moles per liter
List the conditions necessary for formation of the magnetite film on stainless steel
Greater than 400ﾟF and no dissolved oxygen
State the definition of general corrosion
A uniform dissolution or attack of a metal from all surfaces in contact with water.
How do we prevent boric acid corrosion wastage
Minimize RCS/boric acid leaks
Cladding carbon steel or substituting stainless steel
What are the steady state chemistry limits for dissolved oxygen, chloride, and Fluoride.
Dissolved oxygen less than .1 PPM
Chloride less than .15 PPM
Fluoride less than .15 PPM
How is hydrogen embrittlement bad for zircaloy
Diffuses into the zircaloy resulting in a loss of ductility tensile strength
What are the 7 different types of corrosion
Galvanic
Crevice
Pitting
Chloride stress
Fluoride stress
Caustic stress
Boric acid corrosion wastage
Define CRUD
Crud is the metal oxides deposited or suspended in the reactor coolant system
State the benefits gained from general corrosion
If general corrosion results in a film of magnetite being created this will slow down future corrosion as ferrous ion’s must pass through the hard film to react with water
list 3 undesirable characteristics of CRUD
Reduced heat transfer
Collects and then provide a higher radiation source term
Block flow passages or foul demineralizer surfaces
State the means by which CRUD burst are initiated
1) Change the solubility of crud either by ph, temperature, or dissolved oxygen changes
2) Mechanical shock (water hammer) (fluid velocity changes)
Is what is galvanic corrosion
dissimilar metals are in contact in an electrolyte
What is crevice corrosion
Localized attack at or in a mechanical crevice
What is pitting
A deep attack on or in a small area of the metal
What is chloride stress
Intergranular corrosion which occurs in high temperature water, stainless steel and the presence of oxygen and chlorides
