Corrosion Resistance & Coatings Flashcards
7 cards from real CFS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Corrosion Resistance & Coatings flashcards as text
The galvanic series ranks metals by their:
Answer: Electrochemical potential in a given electrolyte
The galvanic series ranks metals and alloys by their electrochemical potential (corrosion potential) measured in a specific electrolyte such as seawater.
Which surface treatment is recommended per ASTM F3125 to prevent hydrogen embrittlement in Grade A490 structural bolts?
Answer: No electroplating; mechanically deposited or organic coatings preferred
A490 bolts must not be electroplated due to hydrogen embrittlement risk; ASTM F3125 permits only mechanically deposited zinc or approved organic coatings.
In a bimetallic couple between steel and copper in a saltwater environment, which metal acts as the anode and corrodes?
Answer: Steel, because it is less noble (more active)
Steel is less noble (more anodic) than copper on the galvanic series, so it acts as the anode and corrodes preferentially in the couple.
Which specification covers the requirements for hot-dip zinc coating of hardware items such as nuts, bolts, and washers?
Answer: ASTM A153
ASTM A153 covers the zinc coating (hot-dip) of iron and steel hardware including threaded fasteners and washers.
Passivation treatment of stainless steel fasteners per ASTM A967 is intended to:
Answer: Remove surface iron contamination and optimize the chromium oxide passive film
Passivation per ASTM A967 uses nitric or citric acid solutions to dissolve free iron from the surface and promote a uniform, dense chromium oxide passive layer.
Which coating is most commonly specified for fasteners used in pressure-treated (ACQ) lumber to prevent accelerated corrosion from the wood preservative chemicals?
Answer: G185 hot-dip galvanizing or stainless steel
ACQ pressure-treated lumber contains copper compounds that are highly corrosive to standard zinc plating, requiring heavy hot-dip galvanizing (G185) or stainless steel fasteners.
The 'area effect' in galvanic corrosion refers to the principle that:
Answer: A small anode coupled to a large cathode corrodes much faster than a large anode with a small cathode
A small anode (e.g., a steel fastener) connected to a large cathode (e.g., a copper plate) results in concentrated corrosion current density on the anode, causing rapid failure.