Steelwork
Most coating failures
Most coating failures
result from poor or inadequate:
result from poor or inadequate:
•
• Steel preparationSteel preparation
•
• CleaningCleaning
•
• Surface preparationSurface preparation
• • ApplicationApplication • • AccessAccess • • VentilationVentilation •
• Coating selectionCoating selection
•
• Inspection and controlInspection and control
•
• Premature exposurePremature exposure
(Exposed too soon)
Investigation by a Guarantee
Investigation by a Guarantee
Insurance company has shown:
Insurance company has shown:
••
95
95 %
% of
of all
all coating
coating failures
failures result
result from
from
––
Poor surface preparation
Poor surface preparation
––
Poor application
Poor application
••
85
85 %
% of
of all
all failures
failures appear
appear within
within 1-2
1-2 years
years
This fits in well with
Rounding or smoothing of: Rounding or smoothing of:
Sharp Sharp edgesedges
CornersCorners
WeldsWelds Grinding of: Grinding of:
LaminationsLaminations
Flame Flame cut cut edgesedges
Weld Weld spatterspatterSteelwork preparation
Steelwork preparation
involves the following activities
involves the following activities
Notches minimum diameter: 30 mm Notches minimum diameter: 30 mm
Inspected and approved before cleaning Inspected and approved before cleaning
See ISO 8501
Coating applied to a square-cut section Coating applied to a square-cut section
Steelwork preparation
Steelwork preparation
Rounding sharp edges
Rounding sharp edges
Reduced coating thickness at
Reduced coating thickness at
sharp edges due to tension
sharp edges due to tension
created during drying / curing
created during drying / curing
Coating Coating Sharp edge Sharp edge Rounded edge Rounded edge Even coating Even coating thickness thickness
Steel
Steel
Manholes in a Tank
Manholes in a Tank
• •Section
Section
manholes
manholes
••
Well grinded
Well grinded
edges
edges
Cd-4932-13 Cd-4932-13
Weld with pinhole.
Weld with pinhole.
Visible through the paint system
Visible through the paint system
•
• Will lead to initiation of corrosionWill lead to initiation of corrosion
•
• Remedial actions: Remove the paint, re-weld and grind. Remedial actions: Remove the paint, re-weld and grind. ApplyApply
paint paint Cd-4930-42 Cd-4930-42 NOTE: NOTE:
Such defects may
Such defects may
be difficult
be difficult to findto find
during inspection
Early corrosion on
Early corrosion on
sharp edge and spot welds
sharp edge and spot welds
•
• Paint has newly been appliedPaint has newly been applied
•
• Exposed to wind and weather for approximately 2 weeksExposed to wind and weather for approximately 2 weeks
Cd-4930-78 Cd-4930-78
Severe corrosion due to a
Severe corrosion due to a
combination of several effects
combination of several effects
•
• Sharp edgesSharp edges
•
• Rough welds (not grinded)Rough welds (not grinded)
•
• Missing stripe coatingMissing stripe coating
Cd-4930-71 Cd-4930-71
Construction after steelwork preparation.
Construction after steelwork preparation.
Grinded edge and weld
Grinded edge and weld
•
• Sharp edgeSharp edge
has been
has been
rounded
rounded
•
• Welding fluxWelding flux
and smoke has
and smoke has
been removed
been removed
•
• Grinded weldGrinded weld
bead
bead
Cd-4932-15 Cd-4932-15
Construction with sharp edge,
Construction with sharp edge,
weld flux and weld beads
weld flux and weld beads
Pre-blasting preparationPre-blasting preparation
to be carried out:
to be carried out: •
• Round sharp edgeRound sharp edge
•
• Remove welding fluxRemove welding flux
with water
with water
•
• Grinding of weld beadGrinding of weld bead
Cd-4932-14 Cd-4932-14
Steel preparation
Steel preparation
Weld spatter, welding smoke
Weld spatter, welding smoke
Weld
Weld
Weld
Weld
spatter
Small weld spatters
Small weld spatters
Even only one small weld spatter may
Even only one small weld spatter may be sufficient to initiatebe sufficient to initiate
corrosion which with time may lead to severe problems
corrosion which with time may lead to severe problems
Cd-4930-45 Cd-4930-45 NOTE: NOTE: Small failures Small failures
like this are
like this are
difficult to find
Cd-4930-39 Cd-4930-39
Unacceptable weld.
Unacceptable weld.
Too rough and full of pinholes/pores
Too rough and full of pinholes/pores
•
• Weld spatters close to weldWeld spatters close to weld
•
• Re-welding and grinding must be carriRe-welding and grinding must be carried outed out
prior to re-blasting and painting
Paint on a very poor weld.
Paint on a very poor weld.
Pinholes and
Pinholes and
holidays visible after second stripe coating
holidays visible after second stripe coating
•
• Neither re-welding nor grinding Neither re-welding nor grinding have beenhave been
carried out prior to application
carried out prior to application •
• Remedial Actions: Re-blasting, re-welding,Remedial Actions: Re-blasting, re-welding,
grinding and blast -cleaning: COSTLY
grinding and blast -cleaning: COSTLY
Cd-4930-41 Cd-4930-41
Early corrosion of welds
Early corrosion of welds
in a water ballast tank
in a water ballast tank
•
• Rough weld seams.Rough weld seams.
Should have been
Should have been
grinded grinded • • Probably inProbably in combination with combination with
poor stripe coating
poor stripe coating •
• Mud can be seen,Mud can be seen,
particularly on the particularly on the bottom bottom Cd-4930-75 Cd-4930-75
Inside a tank after good steelwork
Inside a tank after good steelwork
and paint application
and paint application
Steelwork preparation and application of the paint have
Steelwork preparation and application of the paint have
been carried out well
been carried out well
Cd-4930-51 Cd-4930-51
Steel support after good steelwork
Steel support after good steelwork
and paint application
and paint application
Pre-blasting preparation and application
Pre-blasting preparation and application
of the paint have been carried out well
of the paint have been carried out well
Cd-4930-52 Cd-4930-52
