(a) Suggest two metals that could be used for the cathodic protection of a titanium pipeline. (b) What factors other than relative positions in the electrochemical series need to be considered in practice? (c) Often copper piping is connected to iron pipes in household plumbing systems. What is a possible effect of the copper on the iron pipes?

Understanding the electrochemical series is essential when dealing with various metal interactions, particularly in corrosion and protection methods. This series ranks metals (and some non-metals) based on their tendency to lose electrons, known as their electrode potential.

Metals that are higher in the series, such as magnesium and zinc, tend to lose electrons more readily, making them more reactive. They will corrode or oxidize more easily in the presence of an electrolyte. On the other hand, metals like titanium are lower in the series and hence less reactive.

The practical application of this knowledge, such as in cathodic protection, involves using these rankings to determine which metals will sacrifice themselves to protect others. This is exactly the principle behind using magnesium or zinc to protect titanium pipelines, as shown in our exercise example.

Galvanic corrosion is a type of electrochemical reaction that occurs when two different metals are in electrical contact in the presence of an electrolyte. This setting forms a galvanic cell, where the more anodic metal (higher in the electrochemical series) becomes the sacrificial anode and corrodes, while the cathodic metal (lower in the series) is protected.

The exercise's example of copper piping connected to iron pipes illustrates this point. Copper, being nobler than iron, will not corrode, whereas iron will suffer from accelerated corrosion. This situation is often seen in household plumbing systems and can lead to significant issues if not properly managed with techniques such as dielectric unions or other forms of insulation to prevent the electrical contact.

A sacrificial anode is a strategic component in cathodic protection. It is purposely selected to be sacrificed to protect a more valuable metal structure from corrosion. The anode, made of a metal higher in the electrochemical series than the metal it's meant to protect, deliberately corrodes and thus, spares the other metal from corrosion-induced damage.

For instance, in the case of our titanium pipeline, a sacrificial anode made of magnesium or zinc would corrode over time, protecting the titanium from corrosion. This concept reflects the selfless characteristic of the sacrificial anode, which is an integral part of the cathodic protection strategy. Factors like the anode's lifetime, cost, and availability should also be considered alongside the electrochemical properties for an effective application.

A galvanic cell consists of two different metals connected by an electrolyte, which allows for electron transfer from one metal to the other. It's the basic building block for batteries and the phenomenon behind galvanic corrosion.

When copper and iron pipes are connected, and there's water present (acting as the electrolyte), a galvanic cell is formed where iron serves as the anode and copper as the cathode. This connection causes iron to corrode more rapidly, showcasing a real-world implication of a galvanic cell in everyday materials. Understanding galvanic cells helps in designing systems that prevent unwanted corrosion by avoiding direct electrical connections between dissimilar metals or by implementing appropriate protective measures.