1、5-85SSPC-PS Guide 17.00November 1, 1982Editorial Revisions November 1, 2004SSPC: The Society for Protective CoatingsPAINTING SYSTEM GUIDE NO. 17.00Guide for Selecting Urethane Painting Systems1. Scope1.1 This guide outlines urethane painting systems for structural steel surfaces. There are three typ
2、es of urethane coatings covered by the guide. They are Types II, IV, and V, as classifi ed by ASTM Standard D 16.COMMENT: One-Package Moisture-Cured Urethane Coat-ing (Type II): This coating contains moisture curing isocyanate terminated prepolymers which cure by reaction with moisture from the atmo
3、sphere. Reduced cure rate will result from insuf-fi cient atmospheric moisture (low relative humidity).Two-Package Catalyzed Urethane Coating (Type IV): This coating contains isocyanate terminated prepolymers which cure by reaction with a low molecular weight reactive catalyst. One package contains
4、a prepolymer similar to Type II; the second package contains a relatively small quantity of catalyst to accelerate the room temperature cure. This coating has limited pot life after mixing.Two-Package Polyisocyanate Polyol-Cured Urethane Coating (Type V): This coating contains isocyanate terminated
5、prepolymers which cure by reaction with hydroxyl-bearing polyols. One package contains the isocyanate terminated prepolymers and the second package contains a large quantity of resinous material containing active hydrogen groups. This coating also has limited pot life after mixing.1.2 These painting
6、 systems are suitable for use on parts or structures exposed in varied types of environments rang-ing from severely corrosive environments to mild atmospheric conditions.1.3 These painting systems are intended principally for structural steel where excellent weathering, color retention, and chemical
7、 resistance is desired. The color of the fi nish must be specifi ed.2. Description2.1 This guide outlines the components of a complete urethane painting system. A painting system shall consist of surface preparation by commercial blast cleaning or pickling, one coat of a compatible primer, and one o
8、r more urethane topcoats.3. Referenced Standards3.1 The latest issue, revision, or amendment of the refer-enced standards in effect on the date of invitation to bid shall govern, unless otherwise specifi ed. Standards marked with an asterisk (*) are referenced only in the Notes, which are not requir
9、ements of this specifi cation.3.2 If there is a confl ict between the requirements of any of the cited referenced standards and this specifi cation, the requirements of this specifi cation shall prevail.3.3 SSPC STANDARDS AND JOINT STANDARDS:PA 1 Shop, Field, and Maintenance Painting of SteelPA 2 Me
10、asurement of Dry Coating Thickness With Magnetic GagesPA Guide 3 A Guide to Safety in Paint Appli- cationPA Guide 4 Guide to Maintenance Re-painting with Oil Base or Alkyd Painting SystemsSP 2 Hand Tool CleaningSP 3 Power Tool CleaningSP 5/NACE No. 1 White Metal Blast CleaningSP 6/NACE No. 3 Commerc
11、ial Blast CleaningSP 8 PicklingSP 10/NACE No. 2 Near-White Blast Cleaning3.4 AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) STANDARD:D 16 Terminology for Paint, Related Coatings, Materials, and ApplicationsD 3925 Standard Practice for Sampling Liquid Paints and Related Pigmented Coatings4. Surfac
12、e Preparation4.1 SSPC-SP 6, “Commercial Blast Cleaning,” or SSPC-SP 8, “Pickling.“ If specifi ed in the procurement documents, better degrees of blast cleaning shall be substituted (SSPC-SP 5, “White Metal Blast Cleaning,” or SSPC-SP 10, “Near-White Blast Cleaning”).COMMENT: For new steel, blast cle
13、aning or pickling of the steel is the minimum recommended surface preparation. Better degrees of blast cleaning (SSPC-SP 5 or 10) may be substituted. These methods are more thorough, and the bet-ter cleaning they provide may be more economical or may be required in corrosive conditions. Mill scale i
14、s particularly detrimental to the life expectancy of coatings in immersion or 5-86SSPC-PS Guide 17.00November 1, 1982Editorial Revisions November 1, 2004wet service.In maintenance repainting, if blast cleaning is not feasible, hand or power tool cleaning (SSPC- SP 2 or 3) may suffi ce. These lesser
15、degrees of surface preparation will reduce the service life of the coating system.5. Paints5.1 PRIMERS: After cleaning, the steel shall be primed with one coat of compatible primer.COMMENT: Typical types of compatible primers include organic and inorganic zinc rich, epoxy, universal type copolymer p
16、rimers, urethane, and wash primers.Primers which can be topcoated with urethane coatings are available for use over lesser degrees of surface preparation (SSPC-SP 2, “Hand Tool Cleaning,” or SSPC-SP 3, “Power Tool Cleaning”). Over such cleaned surfaces these primers will perform less effectively.5.2
17、 INTERMEDIATE COAT: Where an intermediate coat is required, it must be compatible with both the prime coat and the fi nish coat, but preferably in a contrasting color. Other generic intermediate coats as recommended by the coating supplier can also be used.5.3 URETHANE TOPCOATS: Aliphatic and aromat
18、ic urethane topcoats can be used.COMMENT: Aliphatic urethane topcoats are recommended where the highest degree of gloss and color retention, along with chemical resistance and recoatability, are desired.Aromatic urethane topcoats are recommended where gloss and color retention are not required, but
19、where chemical and abrasion resistance are desired. Aromatic urethanes require mechanical abrasion prior to recoating.Typical properties of these urethane topcoat types are shown in Table 1.6. Paint Application6.1 PAINT APPLICATION: Follow requirements of SSPC-PA 1, “Shop, Field, and Maintenance Pai
20、nting of Steel.”COMMENT: The primer and all subsequent coats must be compatible. Therefore, before using urethane coatings on previously coated surfaces other than those recommended, compatibility tests should be made for possible lifting or intercoat adhesion problems. Aliphatic urethanes normally
21、have good recoatability while aromatic urethanes require mechanical abrasion prior to recoating.Application may be by brush, roller, air spray, airless spray, electrostatic spray, or a combination of these meth ods. Dipping, fl ow coating, or hot spray is permitted only when specifi cally authorized
22、 by the coating supplier.Some urethane coatings cure at temperatures as low as -7C (20F) and some can be applied as thick as 150 to 200 micrometers (6 to 8 mils) dry fi lm thickness in one application. Drying times and minimum elapsed time permissible between coats of urethane coatings may vary with
23、 type and coating supplier. Particular attention should be paid to these points. Usually, it is good practice to obtain the complete coating system from one supplier.Consult the coating supplier for special handling, industrial hygiene, and storage instructions.6.2 FIELD TOUCH-UP PAINTING: In accord
24、ance with specifi cation SSPC-PA 1, “Shop, Field, and Maintenance Painting of Steel” and in particular with the Section thereof entitled “Field Painting.”6.3 MAINTENANCE PAINTING: For maintenance painting procedures, see SSPC-PA Guide 4, “Guide to Maintenance Repainting with Oil Base or Alkyd Painti
25、ng Systems.”COMMENT: This guide covers the steps necessary for repainting previously painted steel surfaces.6.4 NUMBER OF COATS: A minimum of two.COMMENT: The number of coats will depend upon the service environment, and the recommendations of the coating supplier should be followed.6.5 DRY FILM THI
26、CKNESS OF PAINT SYSTEM: Film thickness shall be measured in accordance with SSPC- PA 2, “Measurement of Dry Coating Thickness with Magnetic Gages.”COMMENT: The recommended dry fi lm thickness of each coat of the complete paint system may vary with the end use and metal surface preparation. Prior to
27、application, the desired thickness of each coat should be agreed upon. The recom-mendations of the supplier should be followed.7. Inspection7.1 All work and materials supplied under this specifi ca-tion is subject to timely inspection by the purchaser or his authorized representative. The contractor
28、 shall correct such work or replace such material as is found defective under this specifi cation (See Note 10.1.). In case of dispute, unless otherwise specifi ed, the arbitration or settlement procedure established in the procurement documents shall be followed. If no arbitration or settlement pro
29、cedure is established, then a procedure mutually agreeable to purchaser, material supplier, and contractor shall be used. 7.2 Samples of paints under this painting system may be requested by the purchaser and shall be supplied upon request along with the manufacturers name and identifi cation for th
30、e materials. Samples may be requested at the time the purchase order is placed, or may be taken from unopened containers at the job site.7.3 Unless otherwise specifi ed, the sampling shall be in accordance with ASTM D 3925.5-87SSPC-PS Guide 17.00November 1, 1982Editorial Revisions November 1, 20048.
31、 Safety8.1 All safety requirements stated in this specifi cation and its component parts apply in addition to any applicable federal, state, and local rules and requirements. Instructions of the paint manufacturer and requirements of insurance underwriters must be considered.8.2 Paints are hazardous
32、 because of their fl ammability and potential toxicity. Proper safety precautions shall be observed to protect against these recognized hazards. Safe handling practices are required and should include, but not be limited to, the provisions of SSPC-PA Guide 3, “A Guide to Safety in Paint Application.
33、”8.3 The paints specifi ed herein may not comply with some air pollution regulations because of their hydrocarbon solvent content.8.4 Ingredients in urethane coatings which may pose a hazard include isocyanates and solvents. Applicable regula-tions governing safe handling practices shall apply to th
34、e use of urethane coatings.8.5 The main items to consider and keep in mind when working with urethane paint systems are as follows: Become informed and aware of the hazards and appropriate control procedures. This can bedone by reading the label, the material safety data sheet, if available, or by c
35、ontacting the supplier of the paint system for other literature and informa- tion. Follow the recommendations prescribed for use during handling and application as set forthby the supplier.TABLE 1RECOMMENDATIONS FOR PHYSICAL AND CHEMICAL PROPERTIES OF URETHANE COATINGSTYPE II TYPE IV TYPE VAliphatic
36、 Aromatic Aliphatic Aromatic Aliphatic (One Package Moisture Cure) (Catalyzed Moisture Cure) (Two Package)Weatherability R LR R LR R LRGloss Retention* R LR R LR R LRColor Retention R LR R LR R LRFlexibility R R R R R RAbrasion Resistance R R R R R RChemical Resistance,(Splash, Spill,Fumes)*Acids (M
37、ineral) LR* LR* LR* LR* LR* LR*Acids (Organic) LR LR LR LR LR LRAlkaline R LR NR NR R LRGases (Atmospheric) R R R R R ROxidizing Agents LR LR NR NR LR LRSolvents R R R R R RSalt Spray R R LR LR R RWeather Resistance R R LR LR R RPerformance Range(Dry) -40 to 120C(-40 to 250 F) R R R R R RLEGEND:R =
38、RecommendedLR - Limited RecommendationNR = Not Recommended*Depends on pigmentation.*For immersion, see supplier.*See supplier for specifi c end-uses.NOTE: Aromatic urethanes are not recommended for outdoor exposure where color and gloss retention are of prime importance.5-88SSPC-PS Guide 17.00Novemb
39、er 1, 1982Editorial Revisions November 1, 2004 Follow all applicable local, state, and federal regulations.8.6 Label information should be available if medical at-tention is required. COMMENT: Toxicological research as well as practical experience has shown that diisocyanates can cause irritation of
40、 the skin, respiratory tract, eyes, nose and throat. In addi-tion, sensitization resulting in allergic dermatitis or asthmatic symptoms can occur following overexposure to diisocyanates. Toxicological research has shown that polyisocyanates have a reduced potential to cause irritation and sensitizat
41、ion relative to their monomeric precursors.Irritation is an acute response which results from the direct contact of isocyanates on the body surface, i.e., skin, mucous membranes of the nasal passages, throat and respiratory tract, eyes, etc. Symptoms usually include watering of the eyes, and a burni
42、ng sensation in the nose and throat. The amount of irritation is dependent upon the dose, tissue exposed and individual susceptibility, but it is generally independent of the individuals exposure history. These acute symptoms are gen-erally reversible soon after the individual is removed from the co
43、ntaminated area or removal of the material from the skin in cases of skin contact.Sensitization is a systemic response and is not limited to the area of contact. Sensitization usually occurs as a result of numerous overexposures or one exposure to very high concen-trations. Both respiratory and derm
44、al sensitization can occur depending upon the toxicologic properties of the diisocyanate, route of exposure and individual susceptibilities. Exposures subsequent to the exposure(s) which actually resulted in sen-sitization may cause a very strong allergic type of reaction. In the case of respiratory
45、 sensitization the reaction is similar to asthma, i.e., coughing, wheezing, tightness in the chest, and shortness of breath. The skin sensitization reaction is allergic dermatitis which may include symptoms such as rash, itching, hives, and swelling of the arms and legs. A sensitized individual may
46、react to extremely low airborne levels even well below the threshold limit value (TLV).If an individual experiences an irritation response while handling an isocyanate it should be determined whether or not the isocyanate was the cause of the irritation. If the isocyanate is the cause, it is an indi
47、cation that the operation, as performed, allows an overexposure to isocyanates which can result in later sensitization of that worker or others. A careful evaluation of the controls, protective equipment, and work practices, should be made to reduce the exposure. If irritation persists in spite of p
48、roper ventilation and protective measures, the individual must be removed from areas where isocyanates are being processed or used.If an individual is sensitized to isocyanates, complete removal from areas of potential exposure is mandated. This is true regardless of whether the isocyanate is presen
49、t in vapor or mist form. Also, exposure to an isocyanate, other than the one suspected of causing the sensitization, must be avoided.Solvents are also present in paints. Prolonged or repeated exposure or overexposure to these solvents by either inhalation or direct skin contact may also cause injurious health effects. The effects are dependent upon the solvent, the extent of exposure, and the route of
