BY SURENDRA SINGH Cor r osion osion Cont r ol Cell Cell
Energy for the World
scuss o
o
• Corrosion Types • • Co Corr rros osio ion n Te Testi sting Me Meth thod ods s
Energy for the World
s
orros on Corrosion is defined as “the chemical or electrochemical reaction between a metal and its environment resulting in r r r .
Energy for the World
Energy for the World
Energy for the World
ec r c em ca ce • Anode : 2Fe 2Fe + + 4e• Cathode : O2 + 2H2O + 4e- 4OHNet Reaction: 2
2
• anode and cathode • n e ec ro y e
Energy for the World
2
3
2
• Corrosion rate is defined in two form
Short Duration Test s per year = ong
Energy for the World
x
x
x
ura on es mm/yr = Thickness loss / time
arame er n uenc ng corros on ra e • Atmospheric exposure – Humidity – – Concentration of salts – moun o a r po u on, ac – pH
Energy for the World
ra n,
r , us e c
ypes o corros on • Uniform Corrosion • Galvanic Corrosion
• Corrosion Fatigue • Stress Corrosion
• Crevice Corrosion • Microbiological
• Erosion Corrosion • Hydrogen Induced Crackin
Energy for the World
•
Uniform corrosion is a form of corrosion in which a metal is attacked at about the same rate over the entire exposed surface.
•
Uniform thickness loss
Energy for the World
tee w t m Mill scale is yellow brownish color in nature and it is loosely adherance with the base metal. After further exposure mill sc le le ds to form tion of rust.
Energy for the World
ca e an
ust
Rust Grade A, as per -
Rust Grade B, as per -
Rust Grade C, as per ISO 8501-1 Energy for the World
Rust Grade D, as per -
a van c • Galvanic corrosion is an electrochemical action of two dissimilar metals in the presence of an electrolyte and an electron conductive path. • It occurs when dissimilar metals are in contact with each other.
Energy for the World
orros on
Energy for the World
Severity of corrosion depends on conductivity of electrol te and anode-cathode area ratio Cathode is more noble than anode and electrol te with good conductivity a o e s more no e an anode and electrolyte with poor conductivity Unfavorable area ratio, Small anode area corrode very rapidly
Energy for the World
•
ng corros on s a oca ze a ac on a material. • The passive film may be destroyed mechanically or b a ressive ions in an electrol te
Energy for the World
• Pitting corrosion occur when the amount of corrosion at one or more points on metal is much greater then the average amount of corrosion. • can be detected by ASTM G48 Standard.
Energy for the World
It occurs mainl in the crevices at the junction of two metals exposed in . Accelerated attack occurs because of a differential in oxygen concentration.
detected by standard ASTM G48.
Energy for the World
Alloys such as austenitic stainless steel & some alloys, when welding results chromium carbide reci itation over rain boundaries. Chromium concentration variation between grain vicinity & grain oun ary, w c n t ate corros on process.
Energy for the World
ASTM No. 7
100X
• Susceptibility of austenitic stainless steel can b d t t d b ASTM A262 • Prevention – Use low carbon content i.e 304L, 316L instead of SS304, 316. – Use Ti or Nb grade SS such as 321, 347.
Energy for the World
ros on
orros on
• The combined action involving corrosion and erosion of metals in the presence of moving through the fluid, leading to accelerated loss of material • The most significant effect of erosioncorrosion is the constant removal of protective film from the metal surface
Energy for the World
Sharp corners creates turbulence, leading to erosion corrosion This corrosion mainly occurs in bends, elbows, valves, pumps, blowers, impellers, nozzle etc.
Energy for the World
The phenomenon of stress the occurrence of microscopic combined action of tensile stress , specific environment.
Energy for the World
SCC causes premature cracking of
Stainless steel
, : Seawater, Acid chloride, H2S
Nickel Alloy
: Caustic soda or NaOH Solution
Susceptibility of metals to SCC can be detected b ASTM G36/NACE TM0177
Energy for the World
ransgranu ar an
Energy for the World
n ergranu ar
cann ng
Tr a n s g r a n u l a r SCC
Energy for the World
ec r n
cr sc py
n t er g r an u a r
orros on a gue defined as a materials failure mechanism which depends on the combined action of repeated cyclic stresses and chemically reactive environment. Corrosion fatigue is a special case of stress corrosion corrosion.
Energy for the World
Hydrogen Embrittlement (HE) causes ductility loss and result in brittle fracture of susceptible materials under applied and residual tensile stresses. ens e stresses, suscept e material, and the presence of y rogen are necessary to cause hydrogen embrittlement. Energy for the World
y r gen n uce • The four essential factors for cracking to occur – uscep e gra n structure: Martensite – of weld – 200oC –
Energy for the World
rac ng
Use low hydrogen welding process a e or eat t e we ng e ectro e e ore we Preheat the metal to remove moisture Reduce stress by heat treatment
Energy for the World
ng
cro o og ca
orros on
•Microbial corrosion is caused by the presence .
bacteria & fungi.
Energy for the World
rr s n
nr
e
s
• Better Material Selection Materials inherently resistant to corrosion in certain environments • Corrosion Control by design • Barrier Protection – Liquid Paints – Powder Coating – • Cathodic Protection – – Galvanic Sacrificial Anode • Energy for the World
• Use material which is not susce tible of corrosion or use high chromium content such as Stainless Steel, Nickel allo instead of carbon steel or mild steel. • Selection process depend on – – Reliability or safety – – Fabrication cost –
• Test the material prior to its usage as per ASTM / Energy for the World
Li q u i d t r a p
o n cr e e Bad Design
Go o d D e si g n
Ba d D e si g n
Concrete Go o d D e si g n
Energy for the World
B a d D e si g n
Go o d D e si g n
Paint Application • It acts as a barrier between the susceptible corrosive metal and the particular environment such as chemical, moisture, sunlight and rain. • Not so costly method and easily applied on the substrate. • B rA h i . • High degree of adhesion with the substrate. • thickness better the corrosion resistance). Energy for the World
ompos on o
Energy for the World
ans
• • Surface Preparation • Mixing and thinning of paint • • Primer layer • Intermediate layer • • Thickness to be achieved Energy for the World
– resins (Vinyl chloride, rubber and acrylic) – a er emu s on a ex oa ng – Oil based Coatings – Epoxy Coatings – – Polyurethanes (isocynate and polyol) – rgan c n r c coa ng
Energy for the World
a Sl No.
Paint Properties Adhesion
1 2
Abrasion/Erosion
3
UV-Resistant
4
5
Energy for the World
Flexibility
Paint continuity
oa
g es
Paint Test
Standard
Cross Cut or Cross Hetch
ISO 2409
Pull-Off Adhesion
D 4541
Taber Test
D 4060
UV-A (340nm) and -
D 4587
Conical Bend Test
ASTM D 522
C lindrical Bend Test
ASTM D 522
Impact Test
D2794
Pinhole/Holiday Test
ISO 5162
Component Name
Exi st in g Paint System
Maint enance Paint system
Interzinc
52 Inter ard 400 Interthane 990 (RAL 7038)
Interplus
Cast Parts / Stator carrier
Intergard
Interplus
a or ng Disc Rotor
Resicoat R4-ES HLF 16R
Interthane
Congard200F
Interplus
Steel Tower
Transformer
Energy for the World
251
ntergar Interthane 990 (RAL 7035)
& Congard 50F Pipcothane MT-300 DACRO-65
256 Interthane 990 Shade - RAL 7038 256 ntert ane Shade - RAL 7035 990 Shade - RAL 7035
256 Interthane 990 Shade - RAL 7038
• Powder coatin is a finishin technology where a decorative and hi hl rotective coatin can be applied to a wide range of roducts. • The process involves spraying , charged particles of pigment coated.
Energy for the World
•
Thermoplastic: • Powder melts and flows to form a film. • Will re-melt when heated. • Thick coating surface • xamp es
•
» Polyethylene » PVC ermosett ng:
• Powder melt flow and cross-link chemically to form film. • Cured coatings have different chemical composition than the basic res ns. • Will not re-melt when reheated • Can produce thin paint like coating of 0.001 – 0.003 inch thick. • Examples » Epoxy » Acrylic Urethane
Energy for the World
• • • • • •
Su erior A earance Corrosion Resistance Highly durable Coating does not drip or sag
or hardners. • Less wastage
Energy for the World
,
,
avanzng • and form a tightly bonded inorganic coating. thickness applied to edges and flat surfaces. • orros on pro ec on mec an sm – Zn layer acts as barrier coating – Zn is more active than steel and corrode first to rotect the cathodic area of the structure.
Energy for the World
a ng
Energy for the World
c ness
a van s ng
Energy for the World
a ng nspec
n
• Coating Thickness – magnetic gauges, optical microscopy (Micron) • Coating Weight – weigh-strip-weigh (g/m2, Oz/ft2) A • – • Additional Tests • – • Bending – bend 180o, diameter = 4Thk
Energy for the World
1mil = 25.4µm = 0.56oz/ft2
Energy for the World
Coutesy by AGA(USA)
surface by making that surface cathode of an . Corrosion Control can be achieved in two ways: 1) Sacrificial Anode 2) Impressed current Cathodic protection is commonly applied on , , platforms. Energy for the World
• Type of sacrif sacrificial icial anod anodes es – Zinc, Al, Mg. • Used Used o on n sma smallll stru structu ctures res • An Anod odes es welde welded d or bolt bolted ed to fixtures • Nee Need d regu regular lar checks checks for wastage
Energy for the World
Involves Involves the use use of an an external external power source – metal metal to be protecte protected d is made made cathodic cathodic to its its surroundin surroundings gs Very costly to run – mainly used in marine appli ap plica cati tion ons s – oil oil rigs rigs – large anodes placed away.
Energy for the World
Corrosion Testing Methods
Energy for the World
• Mainly used to determine resistance of Stainless Steels and • Specimen Size 50mm x 25mm x T • Test Solution : Ferrric Chloride • 2oC • • Measure weight loss after cleaning
Energy for the World
• resistance of Stainless Steels and related allo s • Specimen Size 50mm x 25mm x T mm • Test Solution : Ferrric Chloride • ± 2oC • • Measure weight loss after
Energy for the World
ASTM A262 • Mainly used to determine resistance of austenitic stainless steel to IGC • , grades, such as 304L, 316L, 317L, 321, and , treatments at 650 to 675°C for 1hr.
Energy for the World
• Cutting • • Etching Solution – 10% Electrolytic oxalic Acid
• metallurgical microscope at 250 X to .
Energy for the World
St e p St r u ct u r e
D u a l St r u ct u r e
c Energy for the World
ruc ure
Acid Test • Specimen Size 25mm x 15mm x T mm • es o u on : errr c u a eSulfuric Acid • Test Duration: 120hrs • cleaning and drying Millimeter per month = 7290 x W / A x t x d
Energy for the World
rac ce
—
rc c
• S ecimen Size 25mm x 15mm x T mm • Test Solution : 65 ± 0.2 % b weight Nitric Acid • Test Temperature: Boiling Solution • Test Duration: 48 x 5 = 240 hrs • Measure weight loss W after cleaning and drying • Corrosion rate: Millimeter per month = Energy for the World
es
Sulfuric Acid Test • Specimen Size 100mm x 15mm x 10 mm • Test Solution : Copper-Copper Sulfate-16 %Sulfuric Acid • Test Temperature: Boiling Solution • Test Duration: Min. 24 Hrs • Bend test & Dia : 180O, 4T • Observe the bend surface for cracks, fissure etc.
Energy for the World
-
•
• • • • •
This test method describes procedure for conducting stress-corrosion cracking tests in a boiling magnes um c or e so ut on This test method is applied on cast and welded stainless steel material Test Specimen Size: 100mm x 9mm x 3mm Test Solution: Magnesium Chloride Test Temperature: 155 ± 1oC Test Duration: Min. 96hr Max. 500Hrs using 20X.
Energy for the World
• Used to detect susce tibilit of SS to H2S atmosphere. • 75-85% UTS is a lied to tensile specimen • Test Duration 720 Hrs • Purge H2S gas through inlet tube throughout the test duration • Test temperature 90oC and pressure 16bar • Report the failure of metal
Energy for the World
as per NACE MR0284 • Used to detect pipeline and pressure vessel steel for i ili HI • 3 Specimen of each material of size 100mm x 25mm x T mm • . CH3COOH. Initial pH 2.7 ± 0.1. • Pur e H S as throu h inlet tube throu hout the test duration • Test duration: 96hrs • Cut e ch s ecimen in four rt nd observe for intern l cr cks using microscope.
Energy for the World
a t pray est as per • Widely used corrosion test • Test specimen type, size, duration, evaluation method depends on client requirement • • Test Chamber Temperature: 35 ± 2oC • • If Coated specimen: Observe for blistering, rusting.
• Energy for the World