IS 13643: Test for Corrosivity of Solvent Used for Removal of Water Formed Deposits

16 Pages·1993·1.6 MB·English

by  Bureau of Indian Standards (BIS)

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IS 13643 (1993, Reaffirmed 2008): Test for Corrosivity of
Solvent Used for Removal of Water Formed Deposits. UDC
66.061 : 66.074.3 : 620.193.4
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee””
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”

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(Reaffirmeq. -6a~:~J93
( Reaffirmed 2003 )
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Indian Standard
TEST FOR CORROSIVITY OF SOLVENT
USED FOR REMOVAL OF WATER
FORMED DEPOSITS
UDC 66'061 : 66'074'3 : 620'193'4
<C BIS 1993
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002
March 1993
Price Group 5
. Water-Sectional Committee, CHD 013
FOREWORD
This Indian Standard was adopted by the Buteau of Indian Standards after the draft finalised by
the Water Sectional Committee;had been approved by the Chemica) Division Council.
I nternal surfaces of water steam circuit of any heat exchanger are genera1Jy fouled with water
fonned deposits. For effective and efficient heat exchange, it is necessary to remove these water
formed deposits. Very occasionally, mechanical means !ike· nylon brushing, jet washing are
elnployed to dislodge the deposits, but more often solvent like acid, alkali, mixtures of acids are
invariably utilized to remove the deposits from surface of water steam circuits. However, it is
necessary to examine the solvent before its use whether the same could be detrimental to meta)
surfaces, by way of corrosion.
This standard prescribes the methods of test for corrosivity of solvent before or during use for
removal of water formed deposits. Since. in nlost of the cases it may not be practicable to iso1ate
t
the components of equipment either in full or in part, standard coupons of material of construction
of such equipment would form the basis for evaluating the corrosive attack on industrial
components of equipn1ent.
Different solvents used for removal of water formed deposits shall be as indicated in 0.3 of
IS 12479 : 1988 Methods for analysis of solvent systems used for removal of water formed deposits.
These solvents are categorised as acid, alkali and others.
Acids which are high1y corrosive are generally mixed with suitable inhibitors so that they only
descale the metal surfaces, but do not attack the bare metal. For the purpose of this standard,
inhibitor together with acid will be treated as acid solvent.
In formulation of this standard, considerable assistance has been derived from ASTM G4-84
Conducting Corrosion Coupon Test in Plant Equipment.
In reporting the test result or analysis made in accordance with this standard, if the final value,
observed or calculated, is to be rounded off~ it shall be done in accordance with IS 2: 1960 'R ules
for rounding off numerical values (revised)'.
IS 13643 : 1993
Indian Standard
TEST FOR CORROSIVITY OF SOLVENT
USED FOR REMOVAL OF WATER FORMED
DEPOSITS
1 SCOPE 5 SOLVENTS
1.1 This standard covers the methods of tests for During chemical cleaning process of industrial
corrosivity of solvents/mixture of aqueous solutions equipment for relnoving water fonned deposits, the
of different chemicals used for chemical cleaning following most efficient cOllunercially available
of equipment. solvents or solutions or liquid lllixtures could be
encountered in different environments as indicated
1.2 It also outlines the procedure for qualitative below.
asseSSlllent of degree of corrosion as ready test
nlethods for adopting whenever found necessary. 5.1 Acid Solvents [ Circulation Washing Velocity
Exanullatioll of suitability of solvents, the hazardous/ (1 m/s) ]
safely aspects associated with the use of the chemicals/
a) Hydrochloric acid (5 percent m/v) mixed with
solvents are not covered.
suitable inhibitor at a tClnperature of 65 :t
SoC under nuJd steel construction for reUlova I
2 REFERENCES
of sc~le including corrosion products.
The Indian Standards listed below are the necessary b) Anulloniated citric acid (3 percent ill/V) mixed
adjuncts to this standard: with suitable inhibitor at a temperature of
90°C under austillitic steel or non-ferrous
IS No. Title alloys construction for removing thin layer
scale and corrosion products at variable pH
1167] 1985 Glossary of terms relating to
3.5 to 4 for oxides of iron and at high pH
hojJer water
9.5 to 10 with anullollia for copper removal
12479 1988 Methods of analysis of solvent using suitabJe oxidizing chemical such as
systems used for the removal of potassium bromate, sodium nitrite, hydrogen
water fonned deposits peroxide etc.
c) Compounds based on che1ating agent
3 TERMINOLOGY
(1 percent Ill/V) like EDTA, Triton B, etc,
mixed with suitable inhibitor at 90°C under
For the purpose of this standard, definitions given
austillitic steel or non-ferrous aI10ys
in IS 11671 : 1985 shall apply.
construction for removing thin layer scale
and low degree of corrosion products.
4 LIMITATIONS OF TESTS
d) Sulphonic acid/phosphoric. acid/adipic acid/
4.1 Metal specimens/coupons in a specific solvent phthalic anhydride (2 to 3 percent, m/v) mixed
luay not get corroded at the sanlC rate or in the with suitabJe inhibitor at 90°C under austinitic
same manner as in equipment. Effects caused by steel or non-ferrous alloys construction for
high velocity, abrasiveness, contact time, contact area, removing thin layer scale and low degree
amount of chenlicals, corrosion product, etc, which of corrosion products.
Inay be typical in pipe, elbows, pumps, etc, may
e) Hydrofluoric acid (0.5 to 1 percent, m/v)
not be easily reproduced in coupon tests. Users will
mixed with suitable inhibitor at 65 to 70°C
have, therefore, to establish appropriatc interpretation
in all metal construction for removing most
of coupon test results on their own.
of the scales (excluding calcium) and most
of the corrosion products.
4.2 Coupon corrosion testing is predOJllinantJy used
to describe general corrosion rate. However, specific
NOTE - Optimum temperature as mentioned in the above
type of corrosion may be evaluated by naked eye clauses shall be maintained, as far as possible, throughout the
or by casual inspection or by metallographic
proce~!'.
examination.
5.2 Alkali Solvents
4.3 A well designed coupon progranmle should give
results within appreciable limits which can relate to a) Solution of trisodium phosphate (0.1 percent
the existing material of construction and the solvent mlv) mixed with suitable surface active agent,
lIsed for removing deposit from its surfaces. at 130 to 140°C under mild sled surfaces
IS 13643 : 1993
for relnoving oil borne matters, organic characteristics are desirable to facilitate comparing
species and silica deposits. data from different tests.
b) Solution of caustic soda (0.5 percent, m/v)
7.3.2 After cutting, it is necessary that each of the
alongwith 0.5 percent of sodium nitrate at
specimens are coded with some identification marks
60°C under mild steel surfaces for removing
by notching the edge of the specitnens or by stamping
oily matters, thin Jayer of sjjjca deposits, etc.
or embossing 3 tnm high letters or numbers. When
e) Triammonium citrate at a pH of 9.5 to 10 identifications on each of the specinlens are Inarked,
with suita bIe oxidizing agent to remove it is necessary that the specimens are perfectly
copper deposits frotu mi1d steel equipment. cleaned to remove all previously fonned oxides or
films. The stainless steel aHoy specimens are given
NOTE - Optimum temperature as mentioned in the above a surface conditioning using wet 40 grit silicon oxide
clauses shall be maintained, as far as possible, throughout the paper, whereas aU other materials are scrubbed under
process.
a slurry of 53 lnicrou pumic stone with a bristJe
brush. The lead coupons are lnechanically cleaned
6 INHIBITORS
and then polished with soft doth. However, before
abrasive cleaning, the specimens should be degreased
For each of the above solvent different types of
first by acetone or trkh1oroetby]ene vapour.
inhibitors are rCCOll1111ended for use which prevents
the bare metallic surface to react with the solvent
The treatments are completed by hot and cold distilled
in usc. Inhibitors subjected to corrosion test at
water washing, acetone washing and wann air drying
different working <.~onditions shall be used. followed by swabbing and rinsing in hexane to
remove any residual cleaning materials and then
followed by lOOoe air drying. Then the coupons are
cooled in circulating dry air and stored under
7.1 Standard metal coupons of the metals employed
desiccator prior to repeated weighings. The coupons
in industrial equipment from the surface of which
arc wejgbed to 0.10 mg accuracy. Triplicate
water formed deposits are to be removed, are made
specimens are used for important testings and
to establish l:orrosion rates by loss in weight in the
duplicate for all other normal testil1gs.
different solvent environments encountered as
mentioned above.
NOTE - Average surface roughncs..<; values for the exposed
materials should gcneralJy be 0.2 flm for mild steel, low alloy
7.2 Test coupons having a minimum exposed surface steel, cast iron, etc, and 4.0 to 5.0 lun for copper, brass, lead
area of 26 Cl112 (typically 50 cm2) are obtained and and zinc.
prepared as described in 7.3. However, the specimen
8 TEST COUPONS SUPPORT AND SPACERS
should be as large as call be, for convenient
handling depending on the available analytical
8.1 To hold specimens firmly in space inside the
balan(~e and the opemting equipment, that is, laboratory
corrosion fcst rig either singly or jointly and to prevent
corrosion test rig. The test coupons could be either
loss or damage to specimcns, suitable support of
recla llbJl.llar or circular but sufficient thickness
should be allowed to luiniJuize the possibility of corrosion resistant material preferably, of polytctra
fluoro dhylene (PTFE) or metal rod coaled with PTFE
perforation of the specimen during the test exposun.~.
arc provided. Specimens arc generally held by the
\VhiJc prcparjng the coupons, sharp edges are to
hoJd in them, the hold should be made large enough
be avoided as far as possible. Again jf they arc
subjected to severe cold work, they need to be stress for sliding the specinlcn over the supporting rod.
Clamping devices should not be used to support the
relieved.
specimens.
7.3 .Preparation of Test Specimen
8.2 For exposing more than one specinlen on the
7.3.1 The test specimen of required siZt~ from the same holder and to prevent interference of one
material of ('onstruction actually in use of the specimen with the other during the test period, it
industrial process (fre cut either froln phltc if available is necessary that each of the specimen is suitably
or from the equipmcnt sample. A convenient size separated by insulating material like PTFE. These
for a standard corrosion coupon is 38 mill in diameter separators are cailed 'spacl~rs' which also give finn
and 3 to 5 mm in thickness with 11 mm hole at support for tbe specimen without occupying more
the centre of the circular coupon. For a rectangular area,
typl~, the size could be 50 nun x 25 mm x 3 mm.
Other sizes, shapes and thickness for the specimen 8.3 Although there are many ways of supporting and
can be made for special purposes or to comply with spacing the test coupons, these arc generally llladc
the design of a special type of corrosion rack. Usually as per requirement of tests and aCC0J11111odating freely
no specific finish is necessary for the specimen,' in the test exposure apparatus, A typical assenlbly
unless special aspects have to be examined or studied of support and spacers caIkd 'spool rack', which
(like testing on prepassivated sample, machining! is useful for exposing in open vessels such as reactors
polishing to eliminate cold worked metal, etc). and tanks is indicated in Fig. 1. All" materiaJs used
Howevcr, uniformity in surface including its shining in the assembly should be sufficiently corrosion
2
IS 13643 : 1993
resistant to ensure the assembly remaining intact for indicated earlier for renloving water formed deposits
the duration of the test. Also a typical insert rack are placed or circulated as per the operating
as shown in Fig. 2 is desirable for use in pipes or conditions required. Already weighed, prepared
other units which have flanged connections test coupons in duplicate are then properly put in
which a]]ow access to the system. A rack suitable the rack. The specimen rack with test coupons are
for larger dianleter pipes, long length of horizontal then inserted into the exposure apparatus to dip
and vertical pipe called 'Dutchnlan' type rack as into the liquid suitably without touching the walls
shown in Fig. 3 is also employed. A 'Slip in' corrosion of the exposure apparatus. The preferred
rack as shown in Fig. 4 is ideally suited for effecting position of the rack shall be such that drippage of
the entry and removal of corrosion coupons from corrosion products from one specilnen to another
the exposure equipluent when required without is prevented and the flow of liquid, if any, should
affecting the active service. be adjusted accordingly. The same condition of
agitation of the liquid should then be encountered
9 PROCEDURE by aU specimens. Also, the position of different
specimens in the same rack should be such that
9.1 Suitable specimen rack is chosen as per the galvanic reaction due to different Illctals in solution
exposure apparatus in which respective solvent is avoided.
SUPPORT RODS
~6.35-9.53
,.....--------- 300-600 --------~
MOUNTING STRIP
o
o o
END PLATE OPTION
EN O PLATE OPTION
All dimensions in millimetres.
FIG. 1 TYPICAL SPOOL RACK
3
IS 13643 : 1993
rOR UNUSED COUPONS
NOZZLE: ~6.35mm RO
~9.52mm ROD
SOLID DISK TO FIT
WITHIN BOLl CIRCLE
--------04
300-460mm
FOR PIPE LINES
OR NOZZLES IN USE
THIS PLATE MAY BE
SLOTTED OR OTHERWlSE
PERFORATED TO PEPUIT
now
IN PIPE LINES
OR NOZZLES IN USE
(SEE OPTIONS BELOW)-"
rNO PLATr
OPTIONS
L D
-_.+-_ .....
All dimensions in mHlimctres.
FIG. 2 TYPICAL INSERT RACK
9.2 The duration of exposure is based on known divided by the expected corrosion rate expressed in
rates of corrosion of tbe materials or more often luillimetre per year.
by tbe mode of actual operation in removing water
fonned deposits. However, short exposure (as in actual 9.3 After the test exposures for a stipulated period,
opera tion) ma y lead to incomplete study in view of the test coupons are taken out and the condition and
protection given by films on the metal surfaces initially appearance of the holder and specimens together
while extended exposure of more than two weeks with adhesion of any coatings of filIus 011 the
Illay cause for non ll1liform effects such as pitting surface are exanulled and recorded. As a rccord, it
is advisable to have the test coupons photographed,
a nd phase selective corrosion to occur. As per thulnb .
rule, approximate minimum duration of the test in and the loose corrosion product Inechanically
hours should be either 50 divided by expected removed for X-ray, spectrometer, ch~ntical analysis
etc. The test coupons are then carefulJy washed
corrosion rate expressed in lllils per year, or 2000
4
IS 13643 : 1993
TUBULAR SPACERS
TPE-fLUOROCARBON - -----
GASKET AND NUT
80TH ENDS
- COUPON
__ SOmm
~------------150-300---------- ~
min
All dimensions in millimetrcs.
FIG. 3 TYPICAL DUTCHMAN TYPE RACK
with distiUed water and chemically cleaned with where
suitable solvent to relnove soluble lllaterials from =
S mass loss in mg;
the surface of the test coupons, or chemical cleaning
=
methods to remove corrosion products as indicated P density of the test Inaterial, Inglnlm3; and
iAnn nTeaxb lAe a1r, e Ttaob Jbee 2a ppalnide d.T abJe 3 as given in A = exposed area of the test material, nun2•
MLx K
After sllccessi"'e chemical cleaning, the loosened Corrosion rate, nun/year (CR) =
corrosion products are scrubbed off with a wet nylon
bristle brush. The cleaned coupons are washed in where
cold and hot distilled water, dried in wanu air and
then vacuum desiccated before being weighed. K = 31.557 X 106 in seconds per mea n solar
year, and
The effectiveness of cleaning is judged, visually and
duration of exposure period in seconds.
supported by mass loss measurement. Mass loss
results are obtained for one of the two or two of
The above unit for expressing results relate to
the three coupons exposed in each environment prior
corrosion in terms of p~netration damage. However,
to deciding whether the remaining coupon shall be
where the corrosion has been substantially uniform
used for 11letallographic examination or additional
in distribution over thc surface of the specimcn, an
mass Joss evaluation.
evaluation based on mass loss is appropriate, the
2
unit of which is expressed as g/lu /day.
10 RESULTS
10.2 The specimcn should be carefully cxamined
10.1 The material loss is defined as the nlean for type and uniformity of surface attack such as
thickness of the material wasted in corrosion during etchiug, pitting, dealloying or parting, tarnish, film,
an exposure period. Mass loss results obtained from scale, etc. The maximum and minimulll depth of
the tests are converted to value of 'material loss' the pits can be measured with a t~alibrated micrqscope
and 'corrosion rate'. or by the use of a depth ga uge to the nea rest
0.02 mm and not interpolated or extrapolated.
Material loss, nun (ML) :: S/PA Corrosion at or under the insulating spacers is an
5
rLANGE(TO
GAT£ VALVE)
TPE-fLUORQCARBON
SPACER
9.52mm 55 ROD
BONNET FROM
6 . .3Smm S5 ROD 13mm 55 VALVE
(USE WELDING ROD
AND THREAD TO
10/24 ON END) 025-75
mm PIPE
~~
I
DRAIN VALVE
!~ ~_ ___________ 250 ____~ ____~ ~~~----____- -O-PT-I-O-N-A-L---.-L-·4-----600--------_+_ ___________~
flO/24 HANDLE
SS
LOCK NUTS
250------------------~~
All dimensions in millime1rcs.
H(f. 4 TYPICAL SUP IN CORROSION TEST RACK