Corrosion control in Offshore Environments

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Corrosion Control in Offshore Environments

Text of Corrosion control in Offshore Environments

18 JUN 2010

: M Mn+ + ne : O2 + 2H2O + 4e- 4OH-

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(anode) (cathodic) () () (+)

Other reduction reaction In an acid solution In a neutral or base solution

O2 4H 4 e 2H2 O O2 2H2 O 4 e 4OH

One metal only

Two different metal T diff t t l

Cathodic site

A Anode Cathode Pt

Anodic site

e-

e-

Gas explosion caused by charged soil (crater size: 15 m x 34 m) due to microbial corrosion of gas pipeline (Carlsbed, New Mexico, USA, Aug. 19, 2000)Source: National Transportation Safety Board (USA) www.ntsb.gov

Cost of corrosion (1998, USA)Highway Bridges Gas and Liquid Transm. Pipelines Waterways and Ports Hazardous Materials Storage Air Ports Railroads Gas Distribution Drinking Water and Sewer System Electrical Utilities Telecommunication Motor Vehicles Ships Aircraft Railroad Cars Hazardous Materials Transport Oil and Gas Expl. And Production Petroleum Refining Chem., Petrochem., Parm. Pulp and Paper Agricultural g Food Processing Electronics Home Appliances $1.5 $20.0 $10 $20 $30 $40 Defense Nuclear Waste Storage $0.1 $0 $2.7 $2.2 $2 2 $0.5 $0.9 $1.4 $3.7 $1.7 $6.0 $1.1 $2.1 $6.9 $6 9 $23.4 $0.3 $7.0 $8.3 $7.0

Total 276 billion $ !! 3.1% of GDP

$5.0

$36.0

g $ Mining $0.1

Corrosion Cost and Preventive Strategies in the United States, G.H. Koch, M.P.H. Brongers, N.G. Thompson, Y.P. Virmani and J.H. Payer, FHWA-RD-01-156, Office of Infrastructure Research and Development Federal Hi h F d l Highway Administration, Department of T Ad i i t ti D t t f Transportation, 2003 t ti

Cost of Corrosion Per Analyzed Economic Sector, ($ x billion)

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Most common Corrosive environment evenly distributed over entire metal surface Metal: metallurgically and compositionally uniform On the basis of tonnage waste, the most important forms of corrosion waste Most readily detectable (visual) and preventable (alloying)

Atmospheric corrosion (rusting) Corrosion in acid solutions

TABLE. TABLE Galvanic Series in Seawater (or Fig. 6.1) Fig 6 1)

The galvanic series

Ordered by observed behavior in service Allows for corrosion products Can be defined for alloys Different for every environment Note that some alloys can appear twice acc ording to whether they are active or passive .

Cathodic protection (CP), sacrificial anode protection Galvanized steels; Zn is anodic to steel, act as a sacrificial metal

water-line corrosion

Crevice corrosion of Ti flange in hot seawater

Crevice corrosion of SS

Crevice corrosion of socket weld at gap formed between type 304L pipe And type 316L valve

Chloride pitting of stainless steel due to soldering flux contamination

Pitting of exterior of lead cable sheath due to stray current Carbon steel Pitting Pitti underground

Pitting of Aluminum air duct due to salt contamination Pitting of Inconel in Brine

Sensitization of Stainless Steel or Weld DecayWhen grain boundary Cr carbide preci pitation has occurred, the stainless ste el is said to be sensitized. Sensitization frequently occurs in the h eat-affected zone (HAZ) during welding , and the resultant corrosion is called Weld decay.

Fig. 1.16.

Erosion-Corrosion of a 316L SS flange and pipe (This pump takes its suction about 6m below the surface of the Persian Gulf)

IGSCC of an Inconel heat exchanger tube (500X)

Chloride SCC of S31603 (316L) chemical processing piping system. It can be characterized b th multi-branched t b h t i d by the lti b h d lightning bolt TG crack pattern (300X)

Caustic SCC in a 304L SS pipe in methanol reforming service oxalic acid etch (50X)

Also called: hydrogen induced corrosion (HIC) Involves the ingress of hydrogen into the metal causing Reduced ductility and load-bearing capacity Subsequent cracking and Catastrophic brittle failures at stresses below the yield stress of susceptible ma

terials

Most vulnerable are high-strength steels, titanium alloys and aluminu m alloys

Alloying to resist corrosion (SS, cupronickel, etc.) Metallic coatings (galvanizing) Organic coatings ( i t li i ) O i ti (paint, lining) Electrochemical protection Cathodic protection Anodic protection

Corrosion inhibitors Automotive cooling systems, cooling towers, boilers, etc.

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MATERIAL AND SERVICES Protective Coatings Organic Coatings Metallic Coatings Metals & Alloys Corrosion Inhibitors Polymers (Anodic) Cathodic Protection Services Research & Development R h D l t Education & Training

RANGE ($ x b o ) billion) 33.5-167.5 1.4 14 7.7 1.1 1.8 18 1.97-2.46 1.2 0.020 0 020 0.01 TOTAL $48.7-$183.19

AVERAGE COST ($ x b o ) billion) 100.5 1.4 14 7.7 1.1 1.8 18 2.22 1.2 0.02 0 02 0.01 $115.95 (%) 86.7 1.2 12 6.6 1.0 1.6 16 1.9 1.0