Question 36 UFIV02 - Assistant Engineer - UFIV

The Correct Answer is B **Explanation of Correct Option (B):** Option B states: "Any accumulated scale build-up on sacrificial zinc anodes should be scraped off until the zinc anodes are shiny." This is the correct maintenance procedure because sacrificial anodes (like zinc) work by corroding preferentially (sacrificing themselves) to protect the adjacent, more noble metals (like copper or steel components) from galvanic corrosion. This protection relies entirely on an electrical connection and continuous flow of electrons from the anode (zinc) to the cathode (the protected metal). If scale, barnacles, or paint accumulate on the surface of the zinc anode, it electrically insulates the anode from the surrounding electrolyte (seawater). This insulation prevents the required electrochemical reaction, effectively "killing" the anode and rendering it useless for corrosion protection. To restore the anode's function, the insulating buildup must be removed to expose the active zinc surface, allowing the sacrificial process to resume. **Explanation of Incorrect Options:** A) **Incorrect.** Any accumulated scale build-up (often calcium carbonate or corrosion byproducts) must be removed. Scale acts as an insulator, stopping the flow of current necessary for cathodic protection. Leaving the scale intact ensures *improper* protection and allows galvanic corrosion to damage the protected equipment (the cooler's shell and tubes). C) **Incorrect.** Sacrificial anodes are inspected for *deterioration* (wastage or consumption). They are replaced when they have wasted away significantly (e.g., 50% or more), not solely because of scale buildup. If an anode is still substantial but covered in scale, cleaning the scale off is the correct, cost-effective maintenance action, not immediate replacement. D) **Incorrect.** Scale buildup (fouling, biological growth, or mineral deposition from seawater) is a common and predictable phenomenon in heat exchangers cooled by seawater, especially on cooler surfaces and even on the sacrificial zinc itself. It is entirely possible and must be checked for and addressed.