PCS PCS Corrosion Science and Prevention

Question 1

In electrochemical corrosion, what four components must be present simultaneously for the corrosion cell to function?

Accepted Answer

Anode, cathode, electrolyte, and metallic path

Answer

A complete corrosion cell requires an anode (where metal is lost), a cathode (where reduction occurs), an electrolyte (ionic conductor), and a metallic path connecting anode to cathode.

Question 2

Which form of corrosion occurs when two dissimilar metals are in electrical contact in the presence of an electrolyte?

Accepted Answer

Galvanic corrosion

Answer

Galvanic corrosion occurs when two dissimilar metals form an electrochemical couple in an electrolyte, causing accelerated corrosion of the more active (anodic) metal.

Question 3

What type of corrosion occurs in low-oxygen areas such as lap joints, gaskets, and under deposits?

Accepted Answer

Crevice corrosion

Answer

Crevice corrosion develops in confined spaces where oxygen is depleted, creating an oxygen concentration cell that accelerates localized attack within the crevice.

Question 4

Zinc-rich primers provide corrosion protection to steel primarily through which mechanism?

Accepted Answer

Cathodic (sacrificial) protection by acting as the anode

Answer

Zinc-rich primers protect steel cathodically because zinc is more active than steel in the galvanic series, so zinc corrodes sacrificially to protect the steel substrate.

Question 5

What is the primary cause of osmotic blistering in coatings applied over steel in immersion service?

Accepted Answer

Water-soluble salts trapped under the coating film

Answer

Soluble salts (chlorides, sulfates) beneath a coating draw water through the semi-permeable film via osmosis, creating blisters filled with a corrosive electrolyte solution.

PCS - Protective Coatings Specialist Certification Practice Test

PCS - Protective Coatings Specialist Certification Practice Test

PCS PCS Corrosion Science and Prevention