55.1 General. A variety of systems may have been
applied to old steelwork and it is impracticable to set out detailed guidance for each case. The following notes, however, provide a step-by-step approach.
a) If the existing material and the system are known, obtainable, and have proved satisfactory, it is advisable to use that part of the system which is applicable.
b) The initial film thickness (at least) of the original system should be restored. An additional stripe coat may be desirable at places that have proved particularly vulnerable, such as
expansion-joint edges, bolts, rivets and welds.
c) If for any reason, the existing material cannot be used, specialist advice should be obtained. If this is not available then consideration may be given to the materials listed in 1) and 2) below, provided that they satisfy a test of compatibility with existing materials and that there are no special requirements such as particular resistance to abrasion or chemicals.
1) Surfaces not subject to condensation. External: conventional micaceous iron oxide or chlorinated rubber paint.
Internal: conventional micaceous iron oxide or alkyd paint.
2) Surfaces subject to condensation. External: gelled bitumen or chlorinated rubber paint.
Internal: chlorinated rubber paint
d) Primers that can be overcoated the same day should be used, so that minimum protection can be built up as quickly as possible.
e) The thickness of existing paintwork should be checked with an inspection gauge. Exposure of the previous coat is no guide to thickness.
55.2 Previously painted steelwork. For
previously painted steelwork, the preparations and treatments listed in Table 9 are recommended.
55.3 Previously metal-coated steelwork with
or without additional coating. Where previous
coatings were galvanizing, sprayed zinc or sprayed aluminium, the preparations and treatments listed in Table 10 are recommended.
Table 9 — Treatment of previously painted surfaces
Surface conditions Surface preparation Treatment (see note 7)
[see also 55.1 notes a) to e)] 1. Paint film intact, slight chalking
or checking of top coat only, no significant colour change
Leave alone or wash down only
if a) a) No coating required Bristle brush and dust down if b)
(see note 5) b) Recoating required by legislation or by appearance requirements. Apply one or two finishing coats as required 2. Paint film firmly adherent,
considerable chalking, cracking down to primer or undercoat only, no rusting
Wire brush (see note 5) to remove all loose material and dust down
Intermediate and finishing coats as necessary
3. Erosion or blistering or loss of adhesion at or above substrate and/or light rusting (not worse than Re 3 (see note 4) for thin films)
Scrape and wire brush
(see note 5) to remove rust and loose material
a) Prime any derusted patches. Build up film thickness with appropriate intermediate and finishing coats overall
Thin film (see note 1) b) Patch prime and undercoat derusted patches. Build up film thickness with intermediate coat(s) as necessary. Apply finishing coat overall Thick film (see note 2)
4. Thick film with rusted area less than one quarter (see notes 3 and 8)
a) Rusted patches; remove rust by best means available. See clause 53
Patch prime bare metal
b) Paint conditions 1,2 and 3 as
described above Apply intermediate coat (see note 5) and finishing coat(s) (see note 6) to required thickness c) Sound paint: nil if patching is
adequate
d) Sound paint: wire brush if finish coat is required (see note 5)
5. Thick film with rusted patches greater than one quarter of area (see note 3)
Remove all coating and rust by best means available.
See clause 53
Build up new system of primer, intermediate coat(s) and finishing coat(s)
Thin film rusting worse than Re 7 (see note 4)
NOTE 1 A thin film is defined as one less than 150 µm thick. NOTE 2 A thick film is defined as one greater than 150 µm thick.
NOTE 3 Area is defined as any surface of the structure which is reasonably identifiable for treatment purposes. The condition of all parts of a structure will not necessarily be the same. In deciding the required treatment it is necessary to consider the condition of areas as large as practicable for treatment purposes and deal with each on its merits.
NOTE 4 Re 3 is taken from “Echelle Européenne de degrés d’enrouillement pour peinture antirouille” obtainable from the Paintmakers Association, Alembic House, 93 Albert Embankment, London, SE1 7TY.
NOTE 5 For certain hard finishes special treatment may be necessary to abrade the surface.
NOTE 6 It is a matter of judgement whether to patch paint isolated patches of rust only or to patch paint rusted areas and overcoat the whole. In the latter case it is sometimes desirable, if time permits, to apply additional intermediate coats to bring the patches to a similar thickness to the surrounding areas, before overcoating the whole surface.
94 © BSI 11-1998
Table 10 — Site treatment of previously metal-coated steelwork
Initial
condition Present condition Surface preparation of metal where Replacement
required
Paint treatment over
Sprayed metal Galvanizing
Bare metal coating Areas of corrosion and/or some rusting of substratea If metal is to be replaced, blast-clean Spray metal to appropriate specification, see Table 3 Not normally necessary. If overcoating is required, see Table 3 and 11.3 If metal not to be replaced, clean corroded areas by best means available Not
applicable Build-up cleaned areas with suitable paint system and, preferably, apply chemical-resistant finish overall
Build-up cleaned areas with suitable paint system and, preferably, apply chemical-resistant finish overall Areas with some
white corrosion products
If decoration required wash to remove salts, using stiff brush if necessary. Remove loose material with non-metallic brush
Not
applicable Apply sealing coat and chemical-resistant finish for maximum life Apply suitable surface pretreatment followed by, preferably, chemical-resistant finish If decoration not required, no action
is necessary Not applicable Areas in sound
condition If decoration is required, wash to remove salts, using a non-metallic brush
Not
applicable Apply suitable paint which should be chemical-resistant for maximum life
Apply suitable surface pretreatment; follow by suitable paint which should be chemical-resistant If decoration not required, no action
is necessary Not applicable Sealed or painted metal coating Areas of corrosion or some rusting of substrate If metal is to be replaced, blast-clean Spray metal to appropriate specification, see Table 3 See Table 3 and 11.3, consider one or two coats overall, preferably chemical-resistant
See Table 3 and 11.3, consider one or two coats overall, preferably chemical-resistant If metal not to be replaced, remove corrosion product by best method available Not
applicable Build-up cleaned areas with suitable paint. Apply one or two coats overall, preferably
chemical-resistant
Build-up cleaned areas with suitable paint. Apply one or two coats overall, preferably
chemical-resistant Areas with some
degradation of paint, dissipation of sealer, or loss of adhesion of either Remove loose material with non-metallic brush Not
applicable Apply further coats of paint or sealer, preferably
chemical-resistant
Apply further coats of paint or sealer, preferably
chemical-resistant Areas in sound
condition If decoration is required, dust-down Not applicable As above As above If decoration is not
required, no action
is necessary Not applicable
a It should be confirmed that the apparent rusting emanates from the substrate.
NOTE 1 This section of the code gives recommendations for dealing with typical aspects of safety and health which arise in the work of coating iron and steel structures. It does not give complete coverage of all such aspects, because that is beyond the scope of this code. It is the duty of users of the code, in so far as they are responsible for safety and health, to ensure that all statutory requirements are met.
NOTE 2 The legislative references in clauses 56 and 57 provide a holding position in view of the impending changes in legislation resulting from European Directives. The Framework Directive which will be implemented by the Proposals for Health and Safety (General Provisions) Regulations and Approved Code of Practice and other directives stemming from this means that some of the legislative references (in clauses 56 and 57) may become obsolete.
56 Legislation
56.1 General. A number of Acts of Parliament
contain provisions relevant to surface coating work and these should be taken into account when planning such work. The Acts should be studied directly for detail and coverage, together with any other legislation relevant to particular situations. The Health and Safety at Work etc. Act 1974 imposes a general duty on employers to protect persons at work against risks to health or safety. Note should be taken of The Control of Lead at Work Regulations 1980, The Control of Substances Hazardous to Health Regulations 1988 and the Approved Code of Practice 1988, and Carcinogenic Substances Approved Code of Practice 1988. The Noise at Work Regulations 1989 deal with the legal obligations of employers to prevent damage to hearing.
56.2 Factories Act 1961. The provisions of the
Factories Act 1961 and the Regulations and Orders made under the Factories Act remain in force but are now subject to the enforcement procedures of the Health and Safety at Work etc. Act 1974. The relevant provisions within the Factories Act itself include the following.
Section 131 “Prohibition of employment of women and young persons in painting buildings with lead paint”.
Section 132 “Prohibitions supplementary to sections 129 to 131”.
Relevant Orders and Regulations under the Factories Act include the following.
The Factories (Cleanliness of Walls and Ceilings) Order 1960 (S.I. 1974 as amended by S.I. 1974 No 427) which states the time limits for, and the methods of, cleaning and painting factory interiors.
The Construction (General Provisions)
Regulations 1961 (S.I. 1580), which deal with the
The Construction (Working Places)
Regulations 1966 (S.I. 94), which deal with scaffolding, slung scaffolding, bosun’s chairs, etc. The Construction (Health and Welfare)
Regulations 1966 (S.I. 95), which deal with first aid, washing, toilet and messing facilities. The Construction (Lifting Operations) Regulations 1961 (S.I. 1581).
The Protection of the Eyes Regulations 1974 (S.I. 1681 as amended by S.I. 1875 No. 303) which apply to all surface preparation (except sand papering) and spray painting.
Highly Flammable Liquids and Liquefied Petroleum Gases Regulations 1972 (S.I. 917).
56.3 The Control of Pollution Act 1974. This Act
covers environmental pollution such as noise and the disposal of toxic wastes.