Question

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8 A mild steel water boiler used for dry cleaning service. The dimension of the circular boiler is L= 185cm and D=60 cm. which corrosion prevention would you use to protect and why you choose this method?

Answer 1

Given, the boiler material is mild steel and it is in a cylindrical shape, which has more surface to volume ratio. The major reasons for corrosion are the maximum surface area and acidic exposure to the vessel since in dry cleaning we use chemicals to clean the clothes. So, we can use the Sacrificial anode method.

Reason to use Sacrificial anode method:

• Sacrificial Anodes are used for protection of the hulls of ships, water heaters, pipelines, distribution systems, etc.
• Sacrificial anodes work by oxidizing itself more quickly than the metal of the boiler. That is it gets consumed before the parent metal(boiler metal) reacts with electrolytes. Also specifically, the zinc sacrificial anode was found to be more protective for mild steel specimens.
• It can be effectively used at low and elevated temperatures 27 °C–60 °C for cathodic protection of mild steel.
• The cylindrical boiler is first hot-dip galvanized to prevent corrosion, then a sacrificial anode is attached to the cylinder.
• In soft water conditions, low electrical conductivity of water may reduce the electrical flow between two metals which might stop the anode from corroding causing the cylinder prone to corrosion. But in the dry cleaning little or no water is used. So sacrificial anode is best suitable for corrosion prevention in dry cleaning mild steel boilers.