BAT Material Selection & Properties 3

Question 1

Why is dezincification a critical concern with standard brass backflow preventer bodies?

Accepted Answer

It selectively leaches zinc, leaving a weak, porous copper matrix that can fail structurally

Answer

Dezincification removes zinc from brass alloys, leaving behind a porous, weakened copper structure that cannot maintain pressure integrity, potentially causing catastrophic body failure.

Question 2

Bronze differs metallurgically from brass primarily because bronze:

Accepted Answer

Is an alloy of copper and tin rather than copper and zinc

Answer

Bronze is traditionally an alloy of copper and tin, whereas brass is an alloy of copper and zinc — this composition difference gives bronze superior corrosion resistance in many environments.

Question 3

Stainless steel grade 316 is preferred over grade 304 for backflow assembly components exposed to:

Accepted Answer

Chloride-rich environments such as seawater or coastal applications

Answer

Grade 316 contains molybdenum, which provides significantly better resistance to chloride-induced pitting and crevice corrosion compared to grade 304.

Question 4

Cast iron backflow preventer bodies are MOST vulnerable to corrosion failure when the system water is:

Accepted Answer

Soft, acidic, or aggressive with low pH and dissolved oxygen

Answer

Cast iron corrodes rapidly in soft, acidic, or low-pH water because the protective scale does not form and aggressive water actively attacks the iron surface.

Question 5

Dezincification-resistant (DZR) brass resists dezincification due to small additions of:

Accepted Answer

Arsenic or antimony to inhibit the selective zinc leaching process

Answer

Small additions of arsenic (0.02–0.06%) or antimony inhibit the electrochemical process that causes dezincification in brass alloys.

(BAT) Backflow Assembly Tester Certification Practice Test

(BAT) Backflow Assembly Tester Certification Practice Test

BAT Material Selection & Properties 3