Answers all parts please and show steps clearly Explain why aluminum used as a s

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Answers all parts please and show steps clearly

Explain why aluminum used as a sacrificial anode needs to be kept in a solution of chloride ions. b) Define sensitization. Explain the available methods available for avoiding this effect in welded austenitic stainless steels. (3 + 3) c) Identify what type/types of corrosion cell may be present in the following cases and identify anode/cathode and electrolyte in each case with rough sketches. (1.5 times 4.6) A copper valve in a steel tube exposed to a marine atmosphere. A steel bolt joining two steel plates placed in open air. Revealing the microstructure of a single phase alloy through chemical etching. A galvanized steel pipe underground.

Explanation / Answer

1. the experiment that immersing the alloy of aluminium which is used as sacrificial anode in sodium chloride sloution is called coldworked aluminium sacrificial anode.It shows higher corrision rate and lower corrision potential.In this process the anode also provided a long funcional before it stops working. Coldworks have changed the microstructure of anodes which is suspected in increasing corroision rate and cause depassivate of surface anodes.

2. Sensitization can occur during welding or anneling after cold working.Sensitization is loss of alloy integrity and it reuslts from chromium depletion in the vicinity of carbides precipitated at grain boundaries.This process the steel to become suceptible to intergranular corrision or SCC.

3.1. Galvanic corrision type

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