Corrosion Flashcards
What is pH?
The negative of the base ten log of the hydrogen ion concentration of a solution given in moles per liter.
What is the pH range for the following? Basic. Neutral. Acidic.
Basic is 7-14. Neutral is 7. Acidic is 0-7.
What is General Corrosion?
The uniform dissolution or attack of a metal from all surfaces in contact with water.
What conditions are necessary for the formation of Magnetite?
High Temp (>400). No Dissolved Oxygen.
What is the benefit of general corrosion?
General corrosion forms a film of magnetite, which slows down future corrosion because ferrous ions must pass thru the film to react with water.
How does Temperature affect general corrosion rate?
general corrosion increases at higher temperatures.
How does pH affect general corrosion rate?
General corrosion increases at pH extremes. > 12pH causes caustic embrittlement.
How does Dissolved Oxygen affect general corrosion rate?
Generally the more Dissolved Oxygen the more general corrosion.
List and briefly describe three undesirable characteristics of CRUD.
CRUD will foul heat transfer surfaces, It will tend to collect and then provide a higher radiation source, CRUD may block flow passages or foul demineralizer surfaces.
How are CRUD bursts initiated?
CRUD bursts are caused by changing the solubility of CRUD either by pH( we add Hydrogen peroxide), Temperature or Dissolved oxygen changes. It can also be caused by mechanical shock (water hammer, fluid velocity changes).
What is Galvanic corrosion?
The attack of a metal which results when two dissimilar metals are in contact in a electrolyte.
What is Crevice corrosion?
a localized attack at a mechanical crevice. the crevice becomes a concentration cell.
What is Pitting corrosion?
a deep attack in/on a small area of the metal.
What is Chloride Stress corrosion?
corrosion which occurs in high temperature water where stainless steel and the presence of oxygen and chlorides.
What is Fluoride stress corrosion?
Corrosion which occurs in high temperature water where stainless steel and the presence of oxygen and Fluorides.
