Sea Water Corrosion

lead

grit blasted and covered with organic zinc or metal sprayed zinc coating of enough thickness like upto 0.010" thick and finish coated with solvent epoxy that will also enter the pores of the sprayed coating on ms or cs pipes. You do not use 304 or any other stainless steel for this purpose, all of them would corrode

vshwn7@aol.com

No..No..No.. remember Zinc becomes sacrificial. It will protect the carbon steel by cathodic protection. When the Zinc is converted it liberates Hydrogen gas. The carbon steel, depending where in the water the pipe will be (deep = little oxygen, shallow = moderate oxygen, splash zone = major problem) will absorb the H and cause a condition called Hydrogen embrittlement. Ask the oil guys about this problem, they are still cleaning oil up off the cost of Africa. Now you need to remember the welds when joining the sections. No matter what alloy you use the chlorides will attack the heat affected zone of the joint unless you solution anneal them. Ask the oil guys about this problem, they are still cleaning oil up off the cost of Africa. If you have a short and not to deep application then plastic will work. If the application requires the strength of steel then use a composite coating system (a chrome nickel type). I know that Exxon is working with one in Huston with good results. And its not Zinc or cheep.

Nice answer NICRMONOMORE.

Apparently you stayed awake during the galvanic series lecture.

Congrats on your first"rated good answer"

milo

no to 304 or 430.

For heat exchangers, we frequently see 90-10 Cu-Ni specified in marine applications.

An excellent link for your review follows:

http://www.copper.org/applications/marine/seawater/seawater_corrosion.html

Also, we recommend using the services of a qualified metallurgist whenever possible.

I hope this helps.

The most trusted ( and perhaps the cheapest to last up to fourty years or longer even under tropical sea water condition ) is :

a.sand blasting of the pipe if it is an API standard i.e. normalpipe line steel, then

b.use gunited cement (with high air pressure gunite -cement in strong mix -with sand.

The coating should be at least 7 to 10 centimeters thick and as evenly spread as possible around the pipe. If there are joints, with flanges, these should be -after bolting - also treated with the same technique.

If all of it is well done it will still be active well beyond fifty years.

Labor Omnia Vincit

Hi all,

Not all SS corrode in sea water. What about duplex type SS (2000 series)?

A parameter to measure pitting corrosion resistance in chloride environment (like sea water) is what we call PREN (Pitting Resistance Equivalent).

430 ferritic SS has a PREN about 16,5

304 austenitic has 18,1

316 austenitic has 24,1

2304 duplex has 25,6

2205 duplex has 35

2507 duplex SS has 42,5

Plastic pipe will do just fine. PVC, ABS, PE, PP, PVDF etc., etc.

Unless it's still 1973 at that location......

Thanks to All,

"polietilen" = http://en.wikipedia.org/wiki/Polyethylene?

In the Navy we had a chunk of magnesium attached to the sonar dome to draw the corrosive properties of the sea water to it instead of the other sonar components.

Stainless Steel will still corrode in sea water. Not nearly as fast as soft metal materials but it will still corrode.

stainless steel or rather, the chromium in stainless steel is attacked by the chlorine in sea watter and shuould never be used for this purpose. You are far better off using carbon steel pipe. Better yet but much more expensive, copper pipe can be used. The salts in sea water is quite corrosive. You might want to consider some good plastic piping, too, if it can meet your pressure/temperature requirements. If the pipeline is designed properly, expansion should not be a problem.

I think I would take the simple approach

All steel will eventually corrode... 304, 316 etc.. I would definitely use plastic if possible ... pvc or other ....

================================
Note about ss resistance to corrosion:

316 is apparently more resistant to corrosion than 304 at the beginning

but as time passes , 316 shows an accelerated rate of corrosion. Imagine plotting
Time on an X-axis and corrosion on the Y . Initially 316 runs below 304 .. but as time goes by the slope for the 316 curve becomes steeper than the 304 curve ...

it depends on several factors...operating conditions.. if the ambient temperature is not to low and operating pressure not to high then a plastic material is the best choice...criticality of your service.. design life..and so on...

If you need to select a metallic material then cupro-nickel or Duplex (2507) are the best options..

S.

http://www.corrosionist.com