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Types of Corrosion....Effecting on Natural Gas pipes.
2

Types of Corrosion....Effecting on Natural Gas pipes.

Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
I MAY PLEASE BE GUIDED THAT THERE ARE HOW MANY KINDS OF CORROSION.SPECIALLY I WANT TO KNOW THE TYPES OF SUCH CORROSION WHICH EFFECTS ON NATURAL GAS PIPE LINES.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

For a good general resource, try:

"Forms of Corrosion:  Recognition and Prevention", CP Dillon (editor), published by NACE (there are 2 volumes)

The books contain explanations of the 8 forms of corrosion as well as case studies and pictures.

You can find these on the NACE website (as well as other information):  http://nace.org/nace/index.asp

Enjoy!



RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
SIR...NickelMet..THANK YOU...I hope I will be beneficial for
            the ref.you have given..thanks  (Corr.Engineer)
                                             

RE: Types of Corrosion....Effecting on Natural Gas pipes.

NiDI has an 11-page booklet 'Selection guidelines for corrosion resistant alloys in the oil and gas industry.'
This is for producers of 'raw' natural gas and oil products and gives the effects of various amounts of CO2, H2S,NaCl and temperature on the corrosion rates of 13Cr, 316, 22Cr,and several more.  Comments are made about SCC, SSC (sulfide stress cracking),pitting.
Not as thorough as NACE books, but it's free: download at
http://www.nidi.org/index.cfm?fuseaction=details&ci_id=3279

NiDI also has 'A guide for petroleum engineers' (10073)
which you can request be mailed to you (free).

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
Sir...Kenvlach...Thankyou.. I hope I will be beneficial by
the guidance you have given me...thanks   (Corr.Engineer)

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
MAY I KNOW THAT--HOW A GROUND BED BEHAVES IN CATHODIC PROTECTION SYSTEM..THANKS

RE: Types of Corrosion....Effecting on Natural Gas pipes.

1.  The depth of the ground bed is determined by the
    soil properties.  (soil resistivity)

2.  Weight of the inert anodes is determined based on
    anode type and protection life span.  The anodes
    are buried over each other for deep ground beds
    with connecting cables.

3.  Transformer/Rectifier (A/C ---> D/C) has two feeds
    with a tapping to control amount of current flow.
    The positive feed is connected to the inert anodes
    cables via a junction box and the negative feed
    is connected to the buried surface which requires
    protection.

4.  The T/R rating 50/100/200 amps is determined by the
    amount of surface area to be protected.

5.  At times pipeline corridors are bonded to each other
    and bonding stations are in place to measure potential
    readings.

There are several NACE RP's in this regard.

Concerns:

a)  Bonding between the inert anodes and the cables is  
    usually inadquate since it corrodes (isolating the
    anode) prematurely.

b)  Interference is disregarded, along with cable breaks
    and the T/R are over-tapped.  Anodes fry.

c)  A contraversial issue is wether CP systems should be
    isolated or emalgamated.  Personally my preference is
    towards isolation with resistor boxes to control
    interface.

Let me know if you need elboration on any specific since this a broad subject.  Norsok have nice specifications.

Cheers

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
PVRV!
SIR, I AM THANKFUL TO YOU FOR THE PRECIOUS KNOWLEDGE ,YOU HAVE GIVEN. THANKS A LOT

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
P.S.P POINTS IN CATHODIC PROTECTION SYSTEM.
May I know that:-
1.what psp point means?
2.After how much interval psp point to be marked on low pressure and high pressure gas pipelines.
3.how to maintain and mark psp points on the drawings of a particular area or vacinity.
                            Corrosion Engineer.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
P.S.P POINTS IN CATHODIC PROTECTION SYSTEM.
May I know that:-
1.what psp point means?
2.After how much interval psp point to be marked on low pressure and high pressure gas pipelines.
3.how to maintain and mark psp points on the drawings of a particular area or vacinity.
                            Corrosion Engineer.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
P.S.P POINTS IN CATHODIC PROTECTION SYSTEM.
May I know that:-
1.what psp point means?
2.After how much interval psp point to be marked on low pressure and high pressure gas pipelines.
3.how to maintain and mark psp points on the drawings of a particular area or vacinity.
                            Corrosion Engineer.
 

RE: Types of Corrosion....Effecting on Natural Gas pipes.

Sir,As a finishing doc candidate in the field of Cp applications on pipelines:
I have been having the major problem of knowing the factors governing the placement of an anode greoundbed (horizontal, vertical) with respect to the protected line.

I think your expertise will help  me overcome these worries I have been having these years.
Thanks very much.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
Sir,KALPRO
Sorry I am not able to reply yet.you may consult some web site on corrosion.thanks.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

Can anyone tell me the possible and full content requirement of a Corrosion(Carbon Dioxide) Survey(Scope of Work) in a proposed new offshore gas injection project? Using reciprocating compressors and water cooling ect.
To INCLUDE?
a)Pipe & Fitting & Bulk Material, b)Cathodic Protection, c)Gas Composition (Dew Points, d)Spread Sheet for all Applications etc.
e) Chemical Injection?, f)Major Equipments
g) Specifications & Codes?

Can anyone please furnish a sample survey or tell me where to download a case study?
 

RE: Types of Corrosion....Effecting on Natural Gas pipes.

Myapples
You have the title: “Corrosion Engineer” but you are asking about the very basics of Corrosion Engineering. My personal advice would be to go through the book on Corrosion Engineering by P. Body.

Now normally natural gas pipelines are laid under ground and they have asphalt or some other coating on them. Ideally this coating should be enough to prevet corrosion of the pipe surface but under normal circumstances this is not possible because all coatings are pours to some extent.

Why does a metal corrode when it’s in the soil?
Basically it is an established fact that the soil has its own potential, normally around – 0.6 volts and if we place a metal in the soil its potential is normally around – 0.4 volts. We can measure this potential with a half-cell. (The honorable members of the forum may correct me if I am wrong because I am not an expert in the field of corrosion). Now if we leave the metal in this soil the Fe++ ions from the metal would start to come out of the metal and move to the soil and electrons from the soil will move to the metal. It’s like a battery; you have positive and negative plates and also an electrolyte. In order to stop this chemical reaction the best thing to do is to take the potential of the metal below the soil by applying a forced external voltage through a transformer rectifier unit (also called a CP Station). So you have a transformer which steps down the phase voltage to the desirable level and then it is converted to dc with the help of a rectifier. The output can further be adjusted by a variac or a variable transformer connected before the rectifier unit.

The negative lead of the rectifier is connected to the pipeline and the positive to anode bed. The anode bed has a certain number of anodes depending on the conditions of application. The anodes are normally of Magnesium (I think). Once we have this forced CP in place....... What happens is that if the current finds a path in the coating of the pipe to come out it will travel to the anode but now this current will be actually due to electrons flowing to the anode and not Fe++ ions. This means that no metal is lost from the pipeline. The minimum recommended protection level for a pipeline is –0.85 volts, which ensures that Fe++ ions won’t leave the pipeline. On the other hand Positive ions (Mg++) will move from the anode bed towards the pipeline and if it can find its way through the coating it will deposit on the pipe surface and will not allow corrosion to occur. It can be seen that there is a closed loop for the current to flow.

Why apply coating on the pipeline along with CP?
Because if the pipe is bare then a very large amount of current would flow through the transformer which would require huge transformer and rectifier and anode bed. So the better the coating the lesser the CP current.

PSP?
Its pipe to soil potential recorded with a half-cell. Basically voltage readings are taken between the pipe (through a PSP post…(normally 1 km apart) which has a direct metallic connection to the pipe) and the soil. This is to ensure that the potential of the pipe at this point is above –0.85 (i.e. above the minimum protection level) and also that it is not over protected.

Over protection is a detailed topic and cannot be addressed here.


RE: Types of Corrosion....Effecting on Natural Gas pipes.

Sngpl,

Pretty good post, IMO. Couple of corrections-hope I get these right-it's 1AM here.  

The electrons come from the metal itself, not the soil.  They are "liberated" on the surface at cathode sites.  The iron ions leave the surface at the anode sites.

The -.85v is referenced to a Cu/CuSO4 cell electrode.

In impressed CP, the anodes aren't Mg; they're a Pt alloy, usually.  Mg, Zn and Al are used in sacrificial anode CP.

That's enuf for now.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
Thanks to:-
sngpl(electrical)
and to
Metalguy(materials)
             THANKS.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
JIMMETALSCERAMICS,
THANKS FOR GUIDANCE.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

Metalguy,

Kindly do not hold us in suspence :) please indulge
us by addressing the following in your customary  manner that has always gained my recognition:

1.  Half cells (Cu/CuSO4 versus Ag/AgCl)
2.  Data sheet on coating system (CP Disbondment)
3.  NACE-RP-0XXX, (protection level, -1.5 ?)
4.  Coupling of the anodes.
5.  Current dispersion
6.  Soil Characteristics (Sink Anodes (Mg), shallow
                          ground bed, deep ground bed)
7.  Service temperature (anode type)
8.  Polarizing effects on (anodes)
9.  OPtimization (Decay Rate, Mass)
10. Over tapping

Am sure Sngpl would appreciate your feedbback in this matter; and perhaps we can all appreciate the fact that the more we learn the more we aknowledge how little we really know; as myapples has so elegantly shown us.

With Appreciation,

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
PROTECTION TO WATER PIPE LINES
can we cathodically protect?water pipelines and boiler body.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

The only pragmatic solution is galvanized pipe.

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
jim...thanks

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
MAY I KNOW HOW WE CAN COME TO KNOW THAT A PROTECTED NET WORK IS UNDER THE INFLUANCE OF STRAY CURRENTS OR UNDER INTERFERANCE....AND WHAT ARE THE MEASURES TO GET RID OF INTERFERANCE.  I WELCOME YOUR ANSWERS THANKS

RE: Types of Corrosion....Effecting on Natural Gas pipes.

(OP)
may i know how i can  get a good knowledged corrosion magazine free and from where

RE: Types of Corrosion....Effecting on Natural Gas pipes.

I am currently looking at an application using a dilute sulfuric acid slurry with a pH of less than 1.5.  The process may reach 500F and 700psig for extended periods of time.  I am searching for a cost efficient piping material for this application.  Today the large range of products are available, Alloy 20, Hastelly (multiple grades), 904L, Duplex, Super Duplex, Zirconium and Tantilum.  These materials all have different corrsion rates (well published at lower temperatures)and prices.  The process will require extensive field welding.

I would like to hear from others exeriences they have had with similar operating conditions.  Also a publication that may compare corrosion rates at elevated temperatures for a dilute sulfuric acid application.

  

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