6. Common Defects

1 Common defects306. Common DefectsA paint defect is in many cases due to a number ofcauses. In some cases, several Defects may occursimultaneously and hinder the determination of thecauses and redemption achieve good painting work, applicators and sitesupervisors should understand the causes andpreventive measures of Common Defects that occur atdifferent stages of works. They should also be familiarwith the remedial measures that can be taken to rectifyany unforeseen general, paint Defects can occur during: Paint storage; Application, drying and curing; and Service to Table to for details on the causes,preventive measures and remedial methods for thesecommon of pigment to the bottomand failure to Insufficient stirringduring storage Storage for longduration or underexcessively warmcondition Excessive dilution ordilution withunsuitable materialsTable Common Defects During Paint StoragePreventive Measures Store asrecommended bymanufacturer Avoid direct sunlightand long storage Dilute withappropriate thinnersas recommended bymanufacturerRemedial Methods Stir paint to ahomogeneousconsistency Employ mechanicalstirring for heavysettling Move to appropriatestorage conditions asrecommended bymanufacturer Discard paintSkinningFormation of a layer of skin on thecontainer.

2 Use of non-airtightcontainer Poor formulationsuch as lack of anti-skinning agent Storage underexcessively warmcondition Use airtight container Avoid unnecessaryopening of can Store asrecommended bymanufacturer Remove the layer ofskin and stir paint tohomogeneousconsistency Inform manufacturerfor poor formulation Move to appropriatestorage conditions asrecommended bymanufacturerGellingDecreasing viscosity caused bybacterial degradation of the proteinbinder or other thickening is often accompanied by anoffensive odour. Use of contaminatedtools andwater/solvents Mixing of differentbrands or types ofpaints Use clean tools andwater/solvents Avoid mixingdifferent brands ortypes of paints Discard paintcommon defects31 DefectsBleedingLeaching out of the existing Causes Frequent brushing onthe same spot Use of incompatiblecoats or thinnerTable Common Defects During Application, Drying and CuringPreventive Measures Use properapplication method Apply withappropriate coat andthinner in accordancewith manufacturer srecommendationRemedial Methods Allow drying beforepainting over with anappropriate buffer coat (refer tomanufacturer srecommendation)Running/ Sagging/ CurtainingFlowing or dripping of paint fromupper vertical surface to the lowerpart forming a tear-like or wavyappearance.

3 Painting ofexcessively thick filmlayer at one time Excessive dilution Application of glosspaint on existingpaints or surfacewithout sanding Increase frequency ofpainting thin film Lower dilution ratioeven whereoperability is poor Sand and cleanreceiving surfacebefore application Apply withappropriate coat inaccordance tomanufacturer srecommendation Remove paint film,sand, clean andre-paint as in Preventive Measure Wrinkling/ RivellingFormation of undulating wrinklingfilm. Application of thickOil-Alkyd, whichcauses shrinkage ofpaint film. This tendsto occur when dryingis expedited at hightemperatures Painting overinsufficiently driedpaint Sand and cleanreceiving surfacebefore application Apply withappropriate coat inaccordance withmanufacturer srecommendation Avoid painting inthick film Avoid accumulationof paint around bolts,angles, etc. Observe overcoatingintervals inaccordance withmanufacturer srecommendation Remove paint film,sand, clean andre-paint as in Preventive Measure CrawlingSlipping or inability to form a film.

4 Painting over surfacesthat are not prepared, sand, dirt anddust on the surface Sand and cleanreceiving surfacebefore application Apply withappropriate coat inaccordance withmanufacturer srecommendation Remove paint film,sand, clean andre-paint as in Preventive Measure Common defects32 DefectsCratingFormation of small Causes Painting over surfacesthat are not prepared, sand, dirt anddust on the surface Use of contaminatedtools andwater/solventsPreventive Measures Sand and cleanreceiving surfacebefore application Apply withappropriate coat asrecommended bymanufacturer Use clean tools andwater/solventsRemedial Methods Remove paint film,sand, clean andre-paint as in Preventive Measure LiftingAttacking by successive coating onexisting paint. Use of incompatiblecoats, which causeshrinkage of paintfilm or attacking ofthinner on undercoat Observe overcoatingintervals asrecommended bymanufacturer Allow undercoatingto dry beforeapplication ofsuccessive coating Sand and cleanreceiving surfacebefore application Apply withappropriate coat asrecommended bymanufacturer Remove paint film,sand, clean andre-paint as in Preventive Measure Prolonged Drying TimeInability to dry after application.

5 Incorrect mixing Use of defective paint Mix as recommendedby manufacturer Discard paint if it isdefective Remove paint film,sand, clean andre-paint as in Preventive Measure Loss of GlossReduction of lustre on drying causedby severe absorption of undercoat. Application on roughor unclean surfaces Inadequate orexcessive dilution Use of unsuitablethinner Application ofexcessively thin film Result as blushingoccur Drying occurs in thepresence of excessivemoisture andpollutant Increase frequency ofpainting in thin film Paint adequatethickness of film Use appropriatethinner asrecommended bymanufacturer Avoid painting athigh humidity Prepare receivingsurface and applyappropriate sealer Remove paint film,sand, clean andre-paint as in Preventive Measure Common defects33 DefectsEfflorescencea)Migration of alkaline fromcement based materials andcrystallisation on the surfaceas Painting overinsufficiently curedplaster/concreteTable Common Defects During Service LifePreventive Measures Paint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation)

6 Remedial Methods Removeefflorescence,unstable matters andloose paint film Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation) Seal off withcompatible alkaliresisting primerbefore painting In most persistentcases, epoxy-basedpaint has been usedwith good success butat a higher cost Painting oversubstrate s hairlinecracks Paint on substratewith cracks notvisible at awayfrom walls Patch cracks Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation) Water seepagethrough roof,toilets etc Install properwaterproofing systembefore painting. Arrest moisturesource Prepare and treat thesurface Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation) Rise of dampnessfrom ground Install properwaterproofing systembefore painting Treat dampness Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation) Common defects34 Defectsb)Migration of inherent wood gumand resins in Painting overinsufficiently driedtimber Failure to use primerPreventive Measures Paint on receivingsurface with moisturecontent notexceeding 15%(or refer tomanufacturer srecommendation) Apply appropriateprimer to seal thesurface beforepainting with theundercoat andtopcoat Observe overcoatingintervals inaccordance withmanufacturer srecommendationsRemedial Methods Repaint on receivingsurface with moisturecontent notexceeding 15%(or refer tomanufacturer srecommendation)

7 Apply appropriateprimer to seal thesurface beforerepainting with theundercoat andtopcoatc)Discolouration of paintworkon metals. Failure to removeunstable matterduring surfacepreparation Employ good surfacepreparation beforepainting Clean surfacethoroughly beforerepaintingDeterioration / Erosion of Pigment Use of vibrantcolours paint withorganic particles thatare easily susceptibleto UV degradation Use of paint withwater sensitivepigments Use of paint with lowquality emulsions Select colours that aremore stable Use appropriatecoating system Remove powder andunstable matter Repaint withappropriate coatingsystem Select colours that aremore stableYellowing Use of paint withcertain ingredients, yellowing epoxyand alkyd resins,which are easilyaffected by light, heator environmentalcontaminants Use non-yellowingpaints Prepare surface andrepaint with non-yellowing paintsSaponification Use of alkyd-basedpaints on cementbased materials. Thealkalis from thecement attack the oilin the alkyd resin Avoid using alkyd-based paints oncement basedsurfaces Use appropriatecoating system Remove paint workand repaint withappropriate systemcommon defects35 DefectsCauses Use of non-weathering resistantpaintPreventive Measures Use weather resistantpaint for areasexposed to weatheror UVRemedial Methods Prepare surface andrepaint withappropriate systemChalkingNatural ageing of paint.

8 The extentof chalking will depend on paintformulation and surface exposureto weather. Water seepagethrough roof,toilets etc Install properwaterproofing systembefore painting Arrest moisturesource Prepare and treat thesurface Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation)Peeling & Flaking Painta)Moisture related Painting overinsufficiently curedplaster/ concrete Paint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation) Remove efflorescence ,unstable matters andloose paint film Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation) Failure to useprimer/sealer Failure to use etchingprimer for non-ferrous metals Use of poor alkali-resistingprimer/undercoats orinsufficientpenetrative primer Prime/seal all baresurfaces withappropriate primeror sealer Remove all defectivepaint work andprepare the surface Repaint withappropriate systemb)

9 Incorrect Paint System Failure to removeunstable matterduring surfacepreparation Use of water-solubleputty/ poor adheringplaster Employ adequatesurface preparation toremove all unstablematter Surface must beclean, dry and stablebefore receiving paint Remove all defectiveand loose paint film,and unstable mattersuch as plaster etc Prime/seal the surfacewith appropriateprimer/sealer tofurther stabilise thesurface Re-coat withappropriate coatingsystemc)Poor Surface Preparationcommon defects36 DefectsCauses Painting on a warmsurface Moisture migrationthrough paintedsurfacePreventive Measures Paint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation)Remedial Methods Remove defectivepaint and preparesurface accordingly toreceive paint Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation)BlisteringThis is a moisture-relatedphenomenon. The amount ofmoisture and flexibility of the paintfilm determine the size of the blister.

10 Use of detailsthat traps andaccumulates marks areformed when dirtgets washed downalong the sides of thepainted vertical walls,especially onelastomericcoated wall. Avoid details andcoatings that trap andattract dirt Remove defectivepaint and preparesurface accordingly toreceive paint Apply with moredirt-resistant paintsystemStainingIt should be noted that staining maybe attributed to improper design ofthe building and its fa ade. Yellowish-brownstains caused bymoisture It can be anindication ofwaterproofingproblem in otherparts of the building Ensure all potentialwater leakage andcondensation are incheck Arrest moisturesource. Prepare and treat thesurface. Repaint on receivingsurface with moisturecontent notexceeding 6%(or refer tomanufacturer srecommendation). Repaint withappropriate system. Corrosion of metalelements that areattached to, adjacentto or embedded in,another substrate Installation of metalelements that are nottreated Protect and treat allmetal parts fromcorrosion Remove metal partsand treat the metalsurface Clean the walls andprepare the surface toreceive painting Repaint withappropriate systemRust Stainscommon defects37 DefectsCauses Moisture source andretention Employing of detailsthat assist growth ofalgae/fungi:(i)Profile of substrates.