Structural steel that does not require shop paint shall be cleaned of oil and grease with solvent cleaners, and of dirt and other foreign material, by sweeping with a fiber brush or other suitable means. For structural steel that is required to be shop painted, the requirements in Sections 6.4.1 through 6.4.4 shall apply.
Commentary
Extended exposure of unpainted structural steel that has been cleaned for the subsequent application of fire protection materials can be detrimental to the fabricated product. Most levels of cleaning require the removal of all loose mill scale but permit some amount of tightly adhering mill scale. When a piece of structural steel that has been cleaned to an acceptable level is left exposed to a normal environment, moisture can penetrate behind the scale, and some “lifting” of the scale by the oxidation process is to be expected. Cleanup of “lifted” mill scale is not the responsibility of the fabricator, but is to be assigned by contract requirement to an appropriate contractor.
Section 6.4.3 of this Code is not applicable to weathering steel, for which special cleaning specifications are always required in the contract documents.
6.4.1
Unless otherwise specified in the contract documents, the fabricator shall, as a minimum, hand clean the structural steel of loose rust, loose mill scale, dirt, and other foreign matter prior to painting, by means of wire brushing or by other methods elected by the fabricator, to meet the requirements of SSPC-SP2. If the fabricator's workmanship on surface preparation is to be inspected by the inspector, such inspection shall be performed in a timely manner prior to the application of the shop coat.
Commentary
The selection of a paint system is a design decision involving many factors including the following:
- (a) The owner's preference
- (b) The service life of the structure
- (c) The severity of environmental exposure
- (d) The cost of both initial application and future renewals
- (e) The compatibility of the various components that comprise the paint system (surface preparation, shop coat, and subsequent coats)
Because the inspection of shop painting must be concerned with workmanship at each stage of the operation, the fabricator provides notice of the schedule of operations and affords the inspector access to the work site. Inspection must then be coordinated with that schedule so as to avoid delay of the scheduled operations.
Acceptance of the prepared surface must be made prior to the application of the required shop coat(s) because the degree of surface preparation cannot be readily verified after painting. Time delay between surface preparation and the application of the required shop coat(s) can result in unacceptable deterioration of a properly prepared surface, necessitating a repetition of surface preparation. This is especially true with blast-cleaned surfaces. The required shop coat(s) in any paint system is designed to maximize the wetting and adherence characteristics of the paint, usually at the expense of its weathering capabilities. Deterioration of the required shop coat(s) normally begins immediately after exposure to the elements and worsens as the duration of exposure is extended. Consequently, extended exposure of the required shop coat(s) will likely lead to its deterioration and may necessitate repair, possibly including the repetition of surface preparation and shop coat application in limited areas. With the introduction of high-performance paint systems, avoiding delay in the application of the shop coat has become more critical. High-performance paint systems generally require a greater degree of surface preparation, as well as early application of weathering protection for the required shop coat(s).
Because the fabricator does not control the selection of the paint system, the compatibility of the various components of the total paint system, or the length of exposure of the required shop coat(s), the fabricator cannot guarantee the performance of the required shop coat(s) or any other part of the system. Instead, the fabricator is responsible only for accomplishing the specified surface preparation and for applying the required shop coat(s) in accordance with the contract documents.
This Section stipulates that the structural steel is to be cleaned to meet the requirements in SSPC-SP2. This stipulation is not intended to represent an exclusive cleaning level, but rather the level of surface preparation that will be furnished unless otherwise specified in the contract documents if the structural steel is to be painted.
6.4.2
Unless otherwise specified in the contract documents, paint shall be applied by brushing, spraying, rolling, flow coating, dipping, or other suitable means, at the election of the fabricator. When the term “shop coat,” “shop paint,” or other equivalent term is used with no paint system specified, the fabricator’s standard shop paint shall be applied to a minimum dry-film thickness of one mil (0.025 mm). Unless specifically provided for in the contract documents, the properties of the optional shop coat are at the discretion of the fabricator.
6.4.3
Touch-up of abrasions caused by shipping and handling after painting shall be the responsibility of the contractor that performs touch-up in the field or field painting.
Commentary
Touch-up in the field and field painting are not normally part of the fabricator's or the erector's contract.
6.4.4
The fabricator is not responsible for deterioration of the shop-applied paint when the paint is exposed to atmospheric conditions or corrosive conditions that are more severe than the intended use of the paint; or when painted members are stored for unanticipated durations due to project delays not caused by the fabricator. Handling damage or damage during transportation is not the responsibility of the fabricator unless the painted material is under the direct control of the fabricator or a subcontractor of the fabricator.
Commentary
Paint systems are designed by the manufacturer to perform for a specific amount of time in specific environments. The appropriateness of a paint system and its required application is provided in the paint manufacturer’s technical data sheet. If the painted material is used or stored in conditions that are beyond the paint system’s design intent and the fabricator can show that they followed the directions of the paint data sheet, the fabricator is not responsible if the system fails to perform.
It is common practice that the fabricator temporarily stores the painted material at their plant or a third-party coating subcontractor until it is loaded for shipment. Once the painted material leaves the direct control of the fabricator or a subcontractor of the fabricator, the fabricator cannot be held responsible for damage.