Issue date : June 2016

Preparation of steel substrates
The performance of protective coating is significantly affected by the state of the steel
surface immediately before paint application. The principal factors that are known to
influence this performance are (1) the presence of rust and mill scale, (2) the presence of
surface contaminants, including salts, dusts, oils and greases and (3) the surface profile.
This part describes removal of contaminants and preparation grade of welds, edges andother areas, on steel surface with imperfections. Such imperfections can become visiblebefore and/or after secondary surface preparation. The preparation grades are describedin accordance with ISO8501-3:2006

1. Removal of contaminants(1) Oil / Grease
Oil and/or grease on surface shall be removed. This is best done with a water-based, alkaline degreaser,
followed by fresh water hosing (cold or hot).

Surface contaminated with oil and /or grease. Oil / greacse contaminantscause peeling / detatchment.

Peeling of epoxy coating applied overoil / grease contaminants.

(2) Soluble salts
Soluble salts shall be removed prior to application. The surface to be coated shall be hosed with fresh
water and allowed to dry prior to application of the paint system.

(3) Miscellaneous
Visible dust shall be removed with vacuum cleaning.

2. Preparation of steel substrates
Type of imperfection
Description

Illustration

Preparation grades
Ｐ1

Ｐ2

Ｐ3

１：Welds
Welding spatter

Surface shall be free Surface shall be free Surface shall be freeof all loose welding of all loose andof all welding spatterspatter【see a) 】
lightly adhering
welding spater 【seea) and b) 】

Weld ripple/profile

No preparation

Welding slag

Surface shall be free Surface shall be free Surface shall be freefrom welding slagfrom welding slagfrom welding slag

Undercut

No preparation

Surface shall be free Surface shall befrom sharp or deep fredd fromundercuts
undercuts

Weld porosity

No preparation

Surface pores shall Surface shall be free
be sufficiently open from visible pores
to allow penetrationof paint, or dressedout

No preparation

End craters shall be Surface shall be free
free from sharp
from visible pores
edges

Surface shall beSurface shall bedressed (e.g. byfully dressed,grinding ) to remove i.e.smooth
irregular andsharpedged profiles

Key＊１：visible
２：invisible(might open after abrasive
blast cleaning）
End craters

Type of imperfection
Description

Illustration

Preparation grades
Ｐ1

Ｐ2

Ｐ3

２：Edges
Rolled edges

No preparation

No preparation

Edges shall be
rounded with aradius of not lessthan 2 mm(see ISO 12944-3)

Edges made bypunching shearing,sawing or drilling

No part of the edge
shall be sharp; theedge shall be freefrom fins

No part of the edge
shall be sharp; theedge shall be freefrom fins

Edges shall be
rounded with aradius of not lessthan 2 mm(see ISO 12944-4)

１：punching
２：shearing
Thermally cud edges

Surface shall be free No part of the edge Cut face shall beof slag and loose
shall have an
removed and edges
scale
irregular profile
shall be roundedwith a radius of notless than 2 mm (seeISO 12944-3)

３：Surface generally
Pits and craters

Pits and craters
shall be sufficiently
open toallowpenetration ofpaintPits and craters
Surface shall be freeshall be sufficiently of pits and craters
open to allow
penetration of paint

Shelding (Note: InEnglish-language
usage,the terms"silveres"and"hackles" are also
used to describe
this type ofimperfection.

Surface shall be free Surface shall be free Surface shall be freefrom lifted material from visible shelling from visible shelling

Roll overs/rolllaminations/cut
laminations

Surface shall be free Surface shall bee
from lifted material free from visible
rollovers/laminations

Rolled-in
extraneous matter

Surface shall be free Surface shall be free Surface shall be freefrom rolled-infrom rolled-infrom rolled-in
extraneous matter extraneous matter extraneous matter

Surface shall bee
free from visible
rollovers/laminations

Type of imperfection
Description
Grooves and gouges
fromed bymechanical action

Indentaions and rollmarks

Illustration

Preparation grades
Ｐ1
No preparation

Ｐ2
Ｐ3
The radius ofSurface shall be freegrooves and gouges from grooves
shall be not lessthan 2 mm

No preparation

Indenttions and rollmarks shall besmoothSurface shall be freefrom indentations
and roll marks