Galvanic corrosion rate of Fresh carbon steel with rusted carbon steel 1

[vsubramaniyan]

Hi
when carbon steel corrodes the potential increases in the noble direction due to the formation of rust. when a rusted carbon steel is connected with a fresh carbon steel,the rusted carbon steel will tend to corrode the fresh carbon steel due to galvanic corrosion.

My question is
1. what will be the corrosion rate of fresh carbon steel??
2. Is there any data available for these kind of galvanic corrosion?
3. Is there any way to calculate the rate?. assume the condition to be aearted sea water
4. If I assume the corrosion rate what percent i can escalate from normal atmospheric corrosion? 100%,200%, 300%???

Thanks in advance.

 

[mrfailure]

Your basic premise is flawed. You do not achieve a galvanic couple attaching unrusted to rusted carbon steel no matter what. Oxidation pitting does form mini corrosion cells, but relative rates of corrosion can increase or decrease depending on such factors as geometry, whether crevices form, and how much unoxidized material is available for the corrosion reaction.

For corrosion rates, I use the ASM Handbook of Corrosion Data, which has a lot of test data for systems such as you are proposing.

Aaron Tanzer

http://www.lehightesting.com

 

[grampi1]

To calculate the rate you would need both the corrosion current in the connected and polarized condition as well as the anode surface area. Bur basically large cathode (old steel) small anode (new steel) = trouble. I have seen 2-3mm/yr from such situations.