Sacrificial Anode on isolated copper alloy pipe

In summary, a sacrificial anode is a corrosion prevention method used on isolated copper alloy pipes. This technique involves attaching a more reactive metal, such as zinc or magnesium, to the pipe. The sacrificial anode corrodes preferentially, protecting the copper alloy from deterioration. This approach is particularly effective in environments where electrochemical corrosion is a concern, ensuring the longevity and integrity of the piping system. Proper installation and maintenance of the anode are crucial for optimal performance.
  • #1
Ters
5
0
TL;DR Summary
Isolated copper alloy pipe where seawater flows through protected with sacrificial Anode. What reason?
For a seawater cooling system there is a isolated copper alloy pipe where seawater flows through protected with sacrificial Anode.
For galvanic corrosion there needs to be two different metals connected in a presence of an electrolyte, since this isn't the case.
For what kind of corrosion is this anode protecting this pipe?
 
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  • #2
Welcome to PF.

Ters said:
TL;DR Summary: Isolated copper alloy pipe where seawater flows through protected with sacrificial Anode. What reason?

For galvanic corrosion there needs to be two different metals connected in a presence of an electrolyte, since this isn't the case.
What is not the case?
Seawater = electrolyte.
Copper alloy pipe is being protected by;
Sacrificial anode, (zinc?).
 
  • #3
I don't see the reason why this pipe has to be protected, these sacrificial anodes (zinc) are commonly used to prevent galvanic corrosion, but the condition needed for this;
  1. Electrochemically dissimilar metals must be present
  2. These metals must be in electrical contact, and
  3. The metals must be exposed to an electrolyte
are not present. So my question is is there any other way that there can be galvanic corrosion or is this to prevent another type of corrosion?
 
  • #4
What is the sacrificial electrode attached to?
Is there a metal hull, or a propeller nearby?
Why does seawater flow through the pipe? Is there a pump?
What fittings are present at the ends of the copper alloy pipe?
Heating the seawater as it flows through the pipe may change the reactivity.
The two ends of the copper alloy pipe are attached to each other.
There should be a seacock at one or both ends of the pipe. What is the seacock made from?
 
  • #5
Baluncore said:
What is the sacrificial electrode attached to?
Is there a metal hull, or a propeller nearby?
Why does seawater flow through the pipe? Is there a pump?
What fittings are present at the ends of the copper alloy pipe?
Heating the seawater as it flows through the pipe may change the reactivity.
The two ends of the copper alloy pipe are attached to each other.
The pipe is used in a seawater cooling system in an engine where the water is pumped, the pipe is connected on both ends with rubber connectors so it is isolated to other metals. The sacrificial zinc anode is placed within the pipe via a tapped hole where the zinc is on the end of a bolt.
 
  • #6
When seawater runs through the copper pipe, I would expect to find more copper in the outflow than in the inflow water. The copper pipe would gradually dissolve in the seawater, but the sacrifice of the zinc will prevent that loss. The outflow will then contain more zinc, not copper.
 
  • #7
Baluncore said:
When seawater runs through the copper pipe, I would expect to find more copper in the outflow than in the inflow water. The copper pipe would gradually dissolve in the seawater, but the sacrifice of the zinc will prevent that loss. The outflow will then contain more zinc, not copper.
What kind of process drives this dissolution?
 
  • #8
Ters said:
What kind of process drives this dissolution?
Chemistry. Seawater is NOT saturated with copper.
 
  • #9
Learned the hard way:
'Isolated' can be a dangerous assumption. If Isolation is less than perfect... The 'Zincs' won't hurt anything if they aren't required.
 
  • #10
the process may be called 'electrolysis',
which is driven by electrolytic exchange
-meaning it eats the most readily available metal afaik,
the electricity
 

FAQ: Sacrificial Anode on isolated copper alloy pipe

What is a sacrificial anode and how does it work on isolated copper alloy pipes?

A sacrificial anode is a metal that is more reactive than the metal it is protecting, typically made of zinc, magnesium, or aluminum. When attached to an isolated copper alloy pipe, the sacrificial anode corrodes instead of the copper alloy, thereby protecting it from corrosion. This process occurs through electrochemical reactions where the anode oxidizes, releasing electrons that flow to the copper alloy, preventing it from losing material and degrading over time.

Why is it important to use sacrificial anodes on copper alloy pipes?

Using sacrificial anodes on copper alloy pipes is important because it helps prevent corrosion, which can lead to leaks and structural failure. Copper alloys, while resistant to corrosion under certain conditions, can still suffer from localized corrosion, especially in environments with aggressive electrolytes. Sacrificial anodes extend the lifespan of the pipes and reduce maintenance costs by mitigating corrosion effects.

How do you determine the correct size and type of sacrificial anode for a copper alloy pipe?

Determining the correct size and type of sacrificial anode involves assessing the specific environmental conditions, such as soil resistivity and moisture levels, as well as the diameter and length of the copper alloy pipe. The anode's weight and surface area should be calculated based on the expected corrosion rate and the duration of protection needed. Consulting with a corrosion engineer or using industry guidelines can help in selecting the appropriate anode.

How often should sacrificial anodes be inspected and replaced on copper alloy pipes?

Sacrificial anodes should be inspected at least once a year, or more frequently in harsh environments. The frequency of replacement depends on the rate of corrosion and the size of the anode. Typically, anodes should be replaced when they have corroded to about 50% of their original mass. Regular inspections help ensure that the anodes are functioning effectively and that the copper alloy pipes remain protected.

Can sacrificial anodes be used with other types of metals in a piping system?

Yes, sacrificial anodes can be used with other types of metals in a piping system, but care must be taken to ensure compatibility. The anode material should be more anodic than the metals it is protecting to ensure effective corrosion protection. Additionally, the electrical connections and galvanic coupling must be considered to avoid creating unwanted corrosion cells. It is advisable to consult with a corrosion specialist when integrating different metals in a system.

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