Coating Defects-Trouble Shoot of Application Problems - Eric Chia

8/9/2019 Coating Defects-Trouble Shoot of Application Problems - Eric Chia

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For internal use only not to be circulated outside AkzoNobel

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Trouble shooting of application issue


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Marine & Protective oatingsFor internal use only not to be circulated outside AkzoNobel

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Disclaimer


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!ood Application " !ood Perfor#ance

Assu#ing the specification is approved and confir#ed

A final revie$ of specification #ight be re%uired

Follo$ing the application guidelines $ill ensure

opti#u# perfor#ance

ife expectancy $ill be achieved


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Paint #ixing prior to application

'efore #ixing Part A & ' should be heated(

Mechanical stirrer reco##ended for efficient #ixing(

Mix Part A co#pletely

o#bine entire contents of Part ' and #ix thoroughly(


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Paint re%uire#ents for single leg

!uidance $ithout the use of heater block or trace heatedlines

Individual co#ponents should be pre)heated

'ase *+

uring Agent *,

Mixed paint should be - *+)*.

/he Paint lines should be insulated to #aintain paint

te#perature

0eater block or trace heated lines is another option forlo$ te#peratures

1olvent 23 .45 should be available for cleaning of

e%uip#ent in the event of any spray difficulties


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Paint re%uire#ents for plural co#ponent

!uidance $ithout the use of heater block or trace heatedlines

Individual co#ponents should be pre)03A/36

'ase - *+

uring Agent - *,

o#ponents should be 03A/36 in the tanks as directed

on /61

/he Paint lines should be insulated to #aintain paint

te#perature 0eater block or trace heated lines is another option for

lo$ te#peratures

1olvent 23 .45 should be available for cleaning of

e%uip#ent in the event of any spray difficulties


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Application onditions

1teel te#perature Mini#u# -4,>

Maxi#u# steel te#perature? - +,>

Air condition

7elative hu#idity should be controlled

7educed final syste# perfor#ance a#ine

bloo#

Potential for reduced intercoat adhesion in

#ulticoat sche#es


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!ood ;1 Poor 1tripe oat application


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Pit Filling

/he action of the pit filling is to force the#aterial into the pit re#oving all air pockets

/his is carried out $ith a s%ueegee $ith 1F

#aterial before application of the sche#e

/his is best for open pitting

9se of a s%ueegee $ill not co#pletely fill

o#ega pitting

/hese should be opened up by grinding or

repaired using $elding

onventional8#ega


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Pit Filling

=hen using the spray)s%ueegee techni%ue

1pray #aterial

1%ueegee the product over the pits

Allo$ to flo$ into pits for - + #inutes

1pray the full coat over this area

/his gives better cos#etic appearance and pit)filling


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1hutting 6o$n

All e%uip#ent should be thoroughly flushed $ithcorrect cleaning solvent

3 .4 for 3nviroline

8ther cleaners are not suitable and $ill not clean

1trip e%uip#ent do$n 2if necessary5 at the end of eachday and either?

1teep in solvent overnight

Pressure $ash co#ponents to re#ove all paint

residues

If leaving paint in t$in feed e%uip#ent allo$ to cool

under stirring before transport


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Coating defects

'y understanding the causes of defects@ $e canprevent #any(

It is i#portant to understand that #any defects are

inter)related(


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Causes of Coating Defects

45 Poor 1urface Preparation

1urface conta#ination

1urface profile


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5 Poor Application

Mixing 24)pack & )pack5

9se of brush & roller 2lo$ dft per coat5

9se of spraying 2lo$ or high dft per coat5



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*5 Inco#patible Paint 1yste#s eg )pack over 4)pack syste#s

B5 Incorrect syste# for the environ#ent eg Anticorrosive or Antifouling perfor#ance needs

+5 Poor 3ngineering 6esign Inherent design defects 2eg stitch $elding5



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6ry 1pray

/o coalescence and for# a continuous fil#@ paint

#ust still be fluid $hen it reaches the surface(

Target steel

(panel, ship etcSpray

!"n

#et Paint mergingfrom s ra ti .

$vapo"ration of solvent fromatomised droplets before they

can reach the s"rface..

Specific Defects - Application


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1agging & urtaining =eight of paint on a surface is too #uch for the flo$

properties of the paint to support@ due to?)

a5 /oo high thickness applied(

b5 /oo #uch thinner added to the paint(

c5 Not enough thixotropy for expected $ft(

d5 /e#perature too lo$ C solvent too slo$(

Specific Defects - Application


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0ot 1urface Failure

1urface te#perature of hot ite#s is not al$ays

kno$n@ so difficult to specify coatings(

3arly failures include the follo$ing?)

a5


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halking

o##on for epoxies@ as 9; degradation of the resin at the surfacecauses breakdo$n and the release of pig#ent particles(

It is a surface effect only@ and not associated $ith a true failure(

0o$ever@ surface dust #ust be $ashed off before applying further coats(

Specific Defects - Inherent

9; ight

ong

3xposure

9; ight

Most of the coating

is not affected

/he upper layer

is broken do$n

by 9; light


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'listering

aused by?)

painting over #oisture

painting over soluble salts

solvent entrap#ent

coating per#eability to gas

excessive athodic Protection

painting over porous surfaces

Specific Defects Various Causes


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orrosion

Remember :- Paint does not rust!"

aused by?)

re#oval of coating by #echanical action(

lo$ fil# thickness

poor surface preparation



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racking

Fracture of at least the topcoat of paint $ith ageing@

and occurs $hen the substrate and coating expand

and contract at different rates(

As paint fil#s age@ they beco#e harder and less

flexible and so E1o#ething has to give(

/hin fil#s tend to crack less than thick fil#s(



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racking

1teel and

coating layers

expand and

contract at

different rates

Many

te#peratur

e cycles



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racking due to inco#patible

syste# being applied over an

aged intact coating

racking caused byexcessive dft due to

repeat applications over

#any years



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a5 Poor surface preparation or care on application(

b5 Painting over poorly adhered paint(

c5 9se of inco#patible #aterials in a syste#(

d5 3xceeded overcoating intervals(

e5 Incorrect #ixing for )packs(

f5 Application in unsuitable conditions(

g5 Painting at excessive thickness(

h5 Application beyond Pot)ife

Possible Causes of Detachment


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9pdate 3nviroline application

0ave done 3nviroline application trial run $ith

!racoHM)., plural application in 'P Angola in urong

shipyard on 4JC4K Aug ,4,


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6uring application of 3nviroline B,+0/ 6uring application of 3nviroline *.LF)L,


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1praybility $as good but so#e dra$back due to?

1pray stripe coat on difficult to accessCinaccessibleareas 2scallop holes@ edges of stiffeners@ $elds@ etc5(

1hort pot lives of the products 2*.LF)L, in +#ins and

B,+0/ in B+#ins at +deg(5 render difficulty during

stripe coating by brush(

8vercoating interval of #axi#u# Lhrs is not sufficient


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3*, application on sea$ater desalination

vessel in Naning 6ec ,4,


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3nviroline 4B application on pipe in Malaysia)

,4*


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earning experience fro# site application

Purely used air)hose for spraying e%uip#ent)not sharing $ith

blasting hose

9se a standalone co#pressor to ensure 4,,psi input@ J,psi during

spray application

Pre)heat the individual co#ponent to *+deg(

'oth P/A & P/' re%uired agitate $hen spray using plural

co#ponent

irculate the #ixed #aterial back to the dru# to achieve B,deg( at

tip $hen using single airless spray

1trip coat by plural spray @follo$ by brushing(

0eated tracing line or insulate the line


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Coating Defects-Trouble Shoot of Application Problems - Eric Chia