Accelerated Testing of Industrial Protective Coatings

What are Industrial Protective Coatings?

TECHNOLOGY UPDATE NO. 05 – Accelerated Testing of Industrial Protective Coatings

1. Scope
1.1 This document describes only laboratory experiments. In an industrial setting protective coatings are used for a variety of reasons. Service environments for protective coatings may range from a mild atmospheric exposure condition to a severe chemical or immersion setting.

2. Introduction

2.1 APPLICATION OF ACCELERATED TESTING: The application of accelerated testing differs from user to user. Some typical users are described below. The length of exposure of a coating system in any given test depends on the expected durability of the system and on the severity of the testing environment.

2.1.1 Formulators: Formulators use accelerated testing as a method to screen and compare the behavior of test formula­tions. The general goal is to optimize the formulation through experimental design or the typical ladder series. Formulators often employ ladder series in which one or more components in the coating formulation is changed in a controlled fashion.

2.1.2 Manufacturers: Manufacturers use accelerated testing in the same manner as a formulator. In addition manu­facturers use accelerated testing for drawing comparisons between different products, to follow the results of shifts in raw material supply, and to show conformance with the performance requirements of procurement specifications.

2.1.3 End Users: The desire of end-users is to use accelerated testing as a reliable means of predicting long-term performance, but the goal of predicting performance is not achievable at this time, and it may never be achievable. Currently most end-users therefore employ accelerated testing to rank relative performance of competitive products or to screen coating systems for inclusion on qualified products lists.

Coating manufacturers and specifiers frequently use test exposures of coating materials in an attempt to assess the service life of various candidate coating systems before recommending their use. Test exposures are recognized to be a relevant predictor of coating system performance but can take a very long time to complete. Short term accelerated testing is often used to help provide early indications of coating system performance.

Predicting actual performance of a coating system, based solely on short term testing, can be misleading. A typical short term test may not impose on a coating system the unique combination or frequency of stresses that lead to failure in actual use.

2.2 INTENDED USE: This document is addressed to users and specifiers of protective coatings in an industrial setting. It is intended to provide information on the state-of-the-art in the technology of short term, accelerated testing of coatings. This technology update begins with a discussion of the envi­ronment in which coating systems are expected to perform. The specifier may use this update to assist in interpreting the results of certain accelerated tests. A qualitative analysis of the attributes of typical test methods and their relevance to actual exposures is also provided.

3. Referenced Standards
3.1 SSPC AND JOINT STANDARDS:

SP 11	Power Tool Cleaning to Bare Metal
SP 5/NACE No. 1	White Metal Blast Cleaning
SP 6/NACE No. 3	Commercial Blast Cleaning
SP 7/NACE No. 4	Brush-Off Blast Cleaning
SP 10/NACE No. 2	Near-White Blast Cleaning
SP 12/NACE No. 5	Surface Preparation and Cleaning of Steel and Other Hard Materials by High- and Ultrahigh-Pressure Water Jetting Prior to Re-coating

3.2 AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) STANDARDS:
B 117 Standard Practice for Operating Salt Spray (Fog) Apparatus
B 287 Standard Method of Acetic Acid-Salt Spray (Fog) Testing (Withdrawn 1997)
C 868 Standard Test Method for Chemical Resistance of Protective Linings
D 609 Standard Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conver­sion Coatings, and Related Coating Products
D 870 Standard Practice for Testing Water Resistance of Coatings Using Water Immersion
D 1654 Standard Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
D 2246 Standard Test Method for Finishes on Primed Metallic Substrates for Humidity-Cracking (Withdrawn 1992) Thermal Cycle
D 2247 Standard Practice for Testing Water Resistance of Coatings in 100% Relative Humidity
D 2933 Standard Test Method for Corrosion Resistance of Coated Steel Specimens (Cyclic Method) (Withdrawn 1990)
D 4585 Standard Practice for Testing Water Resistance of Coatings Using Controlled Condensation
D 4587 Standard Practice for Conducting Tests on Paint and Related Coatings and Materials Using a  Fluorescent UV-Condensation Light- and Water-Exposure Apparatus
D 5894 Standard Practice for Cyclic Salt Fog/ UV Exposure of Painted Metal, (Alternating Exposures in a Fog/Dry Cabinet and a UV/ Condensation Cabinet)
G 8 Standard Test Methods for Cathodic Disbonding of Pipeline Coatings
G 23 Standard Practice for Operating Light-Exposure Apparatus (Carbon-Arc Type) With and Without Water for Exposure of Nonmetallic Materials. (Withdrawn 2000; Replaced with G 152 to G 153)
G 26 Standard Practice for Operating Light-Exposure Apparatus (Xenon-Arc Type) With and Without Water for Exposure of Nonmetallic Materials (Withdrawn 2000; Replaced with G 155)
G 53 Standard Practice for Operating Light- and Water-Exposure Apparatus (Fluorescent UV-Condensa­tion Type) for Exposure of Non-metallic Materials Withdrawn 2000; Replaced with G 153)
G 85 Standard Practice for Modified Salt Spray (Fog) Testing

G 87 Standard Practice for Conducting Moist SO² Tests

3.3 NACE INTERNATIONAL STANDARDS:
TM0174 Laboratory Methods for the Evaluation of Protective Coatings and Lining Materials in Immersion Service

4. Characteristics of the Service Environment
4.1 TYPICAL SERVICE ENVIRONMENT DESCRIP­TIONS: The specifier should always remember that coating systems subjected to short term testing are applied, and are expected to provide protection, in a real environment. A wide range of service conditions or environments can be defined under which industrial maintenance protective coatings are expected to perform. A description of environmental zones is given in Appendix A. This is taken from Table 3 of Chapter 1, “How to Use SSPC Specifications and Guides,” in the SSPC Painting Manual, Vol. 2 Systems and Specifications.

Many service environments under which a coating system shall per­form are described by the classification system. To be of value, short-term accelerated tests should reproduce and accentuate the stresses imposed on a coating system by the actual service environment. There are some special use categories which are not covered in the environmental zone concept; these include abrasion resistance, marine fouling, graffiti control, mildew resistance, skidding, or high temperature service. Specially designed tests may be needed for such exposures.

4.2 VARIABILITY OF THE SERVICE ENVIRONMENT: With the sole exception of Zone 0 – Dry Interior (Appendix A), none of the environmental zones present a uniform, invariable service environment. All the service environments in Appendix A for which painting is recommended show variations in one or more of the following stresses:

• Temperature – e.g., daily changes, or freezing and  thawing
• Humidity – e.g., morning formation of dew
• Time-of-wetness – e.g., periodic immersion, or rainfall
• Ultraviolet light intensity and exposure time
• Atmospheric pollutants – e.g., SO2/NO2, smog, salt or particulate deposition
• Chemical attack – e.g., exposure to deicing salts, splash and spillage of acids or alkaline agents
• Mechanical Stresses – e.g., chipping by stones, freeze/ thaw cycling.

Natural service environments are as changeable as the weather. To help better replicate the type and frequency of coat­ing failure found in actual use, many accelerated test methods incorporate controlled variations in test conditions.

4.3 DESIRED OUTCOME OF EXPERIMENT: The purpose of the program dictates the scale and nature of tests used to establish the performance of coatings. For example, a coating to be used in submersion would not be tested in the desert sun. Defining the intended service is important in determining the type of test to use in coating evaluation. This entire process is known as experimental design.

5. Experimental Design Parameters
5.1 Although the experimental design follows from the desired outcome, there are a wide variety of options available for consideration. The primary intent of experimental design is to reduce the number of independent variables which might affect and skew the results of the test program.

5.2 VARIABLES CONTROLLED BY EXPERIMENTAL DESIGN

5.2.1 Choice of Substrate: This should be identical with the substrate upon which the coating shall be applied; i.e., if the structure is ASTM A 36 steel, use A 36 steel panels for testing. On certain occasions, special panels may be required that mimic common structural shapes or commonly encountered design or fabrication flaws.

5.2.2 Choice of Surface Preparation: Unless surface preparation is a variable under study in the experiment, the type of preparation should be identical with the type of preparation required for real application. Typical specifi cations for surface preparation for industrial maintenance coatings are given by SSPC-SP 5/NACE No. 1, SSPC-SP 6/NACE No. 2, SSPC-SP 7/NACE No.4, SSPC-SP 10/NACE No. 3, SSPC-SP 11, and SSPC-SP 12/NACE No 5. Typical preparation requirements for sheet metal products are given in ASTM D 609.

5.2.3 Profile: This should be the profile recommended for use with the coating system unless it is a parameter to be examined in the test program.

5.2.4 Choice of Coating Systems: A valid control coating system or set of controls should be employed. Controls are those systems for which well-defined performance expecta­tions are known, both in actual use and preferably within the tests used in the program. Control coating systems spanning a range of performance from poor-moderate through excel­lent should be used. This will help in subsequent ranking of candidate coating performance.

5.2.5Application: This should be the type of application to be employed in actual use and that recommended by the paint manufacturer. Results obtained from use of ideal application methods, producing a defect-free film, will be of less use in assessing how a coating will perform in actual service.

5.2.6 Types of Experimental Design: If each factor in the design is given equal weight, then the design is called full factorial. Full factorial designs can dramatically increase the number of replicate specimens prepared. One can reduce the scope of the experimental design by careful selection of the points within a design at which maximum replication will occur. Such an approach is called a composite or mixture design. When screening coating formulations, a third approach is often taken which provides replication on only one point.

5.2.7 Number of Test Replicates: Replicate specimens are essential. The number of test replicates is governed in part by the type of experimental design. There are a number of operator dependent variations in applied system characteris­tics. To accommodate these uncontrollable variations, multiple specimens are needed for each factor in the experimental design. With very large replicate sets, 20 or more, it can be demonstrated that failures do not all occur at the same time. Dubbed lifetime analysis, this also reflects actual paint per­formance where failures on a large coated surface occur in a sporadic manner. For many comparative studies, a minimum of five to six replicates is appropriate to improve the validity of the data. (Almost all existing performance based specifications call for no more than two replicates.)

TABLE 1A – CORRELATIONS OF TIME TO RUST FAILURES ASTM B 117 SALT FOG VS. KURE BEACH
	Number of Specimens

Paint Systems

Tested

Correlation Coefficient

Degree of Significance

All Systems	56	0.53	>99%
Lead and Chromate in Oil	5	0.63	<95%
Lead and Chromate, Oil-Free	25	0.57	<95%
TT-P-86G, Type II	8	0.95	>99%
Proprietary Pigment #10 in Oil	6	0.334	low
Acrylic	6	0.308	low

Data taken from references 1 and 8 (SSPC).

6. Characteristics of Controlled Accelerated Tests
6.1 CLASSIFICATION OF ACCELERATED TEST METHODS: Accelerated test methods can be classified in accordance with the following criteria:

• Constant stress or cyclic/variable test
• Industry standard test or non-standardized test
• Multi-component stresses or single component stress

Appendix B summarizes the characteristics of many ac­celerated test methods typically used in evaluating industrial maintenance coatings.

6.2 COMMON ACCELERATED TEST METHODS: An ideal accelerated test would expose new coatings to the stresses expected in real exposure, would induce exactly the type of failures observed in real use, and would do so quickly. In reality, this ideal is difficult to achieve.

6.2.1 Salt Spray Testing (ASTM B 117, ASTM B 287): Salt spray testing in accordance with ASTM B 117 and ASTM B 287 exposes panels to constant stresses of temperature (95°F), humidity (100%) and a corrosive salt solution (for ASTM B 117 testing, 5% NaCI is used). Panels are commonly scribed and evaluated for rust, blister, and scribe undercut failure. Typical test durations can run anywhere from 500 hours to 5,000 hours or more. Originally developed for use in testing metallic coatings, ASTM B 117 testing became the method of choice for evaluation of coatings on metal products because of the lack of other suitable test methods.

Salt fog testing in accordance with ASTM B 117 is the most widely used method for screening coating performance. Many specifications include the use of this test. Modes of failure observed are blistering, rusting on the panel face, and scribe undercutting. The rust product created by this test is unlike that found in most atmospheric exposures. Blistering failure is far higher than found in most atmospheric exposures.

Studies have shown that the rankings of coatings in salt fog testing often bear little correlation to rankings from expo­sure in any real atmospheric service. In part this is because the failures are different. The type of reactions occurring on the sample panel are unique to the test chamber; this also causes the discrepancy in results between salt fog testing and real exposure. Table 1 depicts the correlation between salt fog exposures and some typical exposure sites. The data is taken from two studies, SSPCʼs Performance of Alternate Coatings in the Environment (PACE), and a study of the relative merits of constant or cyclic salt spray exposures by the Paint Research Association (PRA).1, 2 The PACE results, Table 1A, show that, with one exception, for subclasses of the full set of coatings tested, poor or low correlation is observed between time to failures by rusting at the marine site, and preliminary screening in ASTM B 117 salt spray. The study at the PRA, Table 1B, used a lower number of coating samples, and also indicates poor correlation between exterior exposure and salt spray exposure. The poor correlation observed is quite typical; note that even the marine site results do not correlate well with ASTM B 117 exposures, especially when waterborne or lead-free coatings were examined.

In some coatings, the high concentration of salt present can induce saponification reactions that contribute to the observed undercutting and blistering failures. Coatings are being tested for their resistance to this unique test environment. Coatings may perform poorly in this test and yet provide good service in outdoor exposures. Despite this anomaly, ASTM B 117 testing continues to be specified and used.

TABLE 1B – PRA TEST SPEARMAN RANK CORRELATIONS1
Comparison Mode	Correlation Coefficient
Exterior vs. Salt Spray	0.18
Exterior vs. Cyclic Salt Spray	0.68
Salt Spray vs. Cyclic Salt Spray	0.65

1 Minimum correlation or 95% confidence requires a correlation coefficient of at least 0.87. Data taken from reference 2 (PRA).

6.2.2 Cyclic Salt Spray Testing (ASTM G 85 Appendix A5): Cyclic salt spray testing involves periodic drying of the panel surfaces following exposure to a salt fog. Unlike ASTM B 117, the salt used is a weak mixture of ammonium sulphate 0.325% and sodium chloride 0.05% and the salt fog exposure takes place under ambient conditions.4 The rapid drying of panels is accomplished by panel heaters and forced air coming into the cabinet. Panel heaters are present in the walls of the cabinet. During the dry cycle the panel heaters are turned on and the temperature in the cabinet rises to 35°C. Ratings and panel preparation are similar to that for ASTM B 117 testing.

This test is claimed to better reproduce macroscopic visual degradation typical of field failures such as rusting and scribe undercutting. It reduces the incidence of underfilm blistering noted in many other test methods. As blistering is little seen in most real exposures, the test is claimed to be more repre­sentative of actual coating performance.

The chemical make up of the rust product is believed to be closer to that found in real exposures. The rust is less crystalline in nature, i.e., more amorphous. The change in character of rust from the ASTM B 117 test is attributed to the constituents and concentrations of the electrolyte and the use of a cyclic exposure. Table 2A depicts the relative performance of a set of ten coatings in cyclic salt spray, salt spray testing in accordance with ASTM B 117, and normal industrial exposure. Accelerated tests were conducted for 1,500 hours and exterior exposures were conducted for 40 months.

The performance of the coating systems was assessed on the basis of undercutting at a deliberately placed scribe defect (see Figure 1 and Table 2B). Scribe undercutting was measured in units of 1 mm in accordance with ASTM D 1654. There are a number of clear discrepancies in the scribe undercutting recorded in the ASTM B 117 exposure when compared with real performance from the field exposure site. The incidence of anomalous poor performance is lower in the cyclic salt spray exposure. When the scribe values from the field data are plot­ted against those from the two accelerated tests, regression line fits can be derived between the two sets of data. These indicate the degree of correlation between the artifi cial test environment and the actual exposure. While the ASTM B 117 test has a lack of correlation with actual exposure, the cyclic salt spray test shows a strong positive correlation to performance at the industrial site, as shown in Figure 1.

The cyclic salt spray test described in ASTM G 85, Appendix 5 is used in combination with ASTM D 4587 expo­sure to create a multi-component exposure defi ned in ASTM D 5894 (see Section 6.2.3.1).

6.2.3 Combination Cyclic Exposures: An approach to producing a cyclic exposure entails combining exposure within different cabinet environments. These combination experiments are similar to the humidity freeze-thaw cycling discussed later. They can be customized experiments with any desired degree of complexity deemed appropriate to mimic actual service.

6.2.3.1 Combined Cyclic Salt Spray UV/Condensation (ASTM D 5894): One recent example of a combination cycle experiment involves both a cyclic salt spray exposure (as defined in ASTM G 85, Appendix A5) and ultraviolet condensa­tion apparatus exposure. Marked improvements in correlation with outdoor exposure are claimed for this experiment. The test developers stress that ultraviolet light exposure is critical to the success of the experiment. Polymer degradation is induced by the UV light, weakening the coating and making it more susceptible to undercutting and blister formation at the scribe. Table 3 and Figure 2 depict the results from this ex­periment. Again scribe undercutting measured in accordance with ASTM D 1654 is used as the measure of coating system performance.

Results are shown for three coating systems exposed in five environments: two natural exposures and three accelerated tests. In addition to the combination cyclic salt spray with ultraviolet condensation, panels were exposed to the previously described cyclic salt spray test and salt spray testing in accordance with ASTM B 117. The exterior exposures consisted of an industrial site and a coastal marine site. Data is presented from ratings after 27 months exposure at the exterior test sites, and the accelerated tests were con­ducted for 2,000 hours.5 NOTE: Durations of exposure for high performance coatings may be longer than those used in the referenced test program.

The data shown in Table 3 have been converted to a deci­mal scale in which a ten indicates no scribe undercutting and a zero indicates 16 mm creepage from the scribe; the scale is defined in ASTM D 1654. Simple examination of the data in Table 3 shows that only the combination cycle experiment, UV/Wet/Dry Test, exhibits a close relationship with the data from the marine exposure site. The relationship between the combination cycle experiment and both marine and industrial exposure is shown in Figure 2; the small data set contributes to the high degree of correlation.

Other early indicators of coating failure suggested by this test include loss of gloss and increase in coating surface rough­ness. The visual appearance of the blisters formed near the scribe is nearly identical with that of the samples exposed in an industrial environment. The relative ranking of four generic coatings was remarkably similar in both the test and actual exposures. (The use of ASTM D 5894 and the independent cyclic salt fog exposure component is only recommended for organic coatings, or coating systems in which inorganic zinc is topcoated with organic topcoats. Direct comparisons of the results of exposure of untopcoated inorganic zinc-rich prim­ers with systems based on organic coatings, or with organic topcoats, are misleading.

TABLE 2A SCRIBE DATA FROM FIELD AND LAB
		Scribe Cyclic	Scribe ASTM B 117
Paint System	Scribe Field1mm/40 months	Salt Spray2 mm/1500 Hours	Salt Spray3mm/1500 Hours
1	14.0	16.0	4.0
2	3.5	2.0	0.0
3	2.0	12.3	32.0
4	3.0	8.3	18.7
5	3.0	7.5	8.0
6	2.0	4.3	4.0
7	1.0	2.0	2.0
8	0.0	0.0	0.0
9	3.5	5.8	3.3
10	3.5	6.4	8.8

¹ Reflects the average of four replicates.

² Reflects the average of four replicates.

³ Reflects the average of three replicates.

Data taken from SSPC internal research project on Advances in the Performance Evaluation of Coatings (APEC). 10-75

6.3 OTHER STANDARD METHODS: Tests other than ASTM B 117, ASTM D 5894, and ASTM G 85 are also used for testing of industrial coatings intended for atmospheric or other ser­vice environments. From surveys which SSPC conducted for the Navy Civil Engineering Laboratory and The Federation of Societies for Coatings Technology, a list of these tests was produced. All the tests listed below are currently used, but less frequently than ASTM B 117 testing.3

• Humidity testing – ASTM D 2247, ASTM D 4585
• Light, Heat and Condensation Exposures – ASTM D 4587, ASTM G 53
• Artificial Weathering – ASTM G 23, ASTM G 26
• SO2/Moisture Exposure – ASTM G 87
• Immersion Testing – ASTM C 868, ASTM D 870, NACE TM0174
• Cathodic Disbondment – ASTM G 8
• Humidity Freeze-Thaw Cycling – ASTM D 2246 (discontinued)

Humidity freeze-thaw cycling has been used in combina­tion exposures that cycle panels between different exposure chambers. One example involved the ASTM D 2246 (discon­tinued) testing used in combination with ASTM B 117 and ASTM D 4587 exposures. With the exception of ASTM B 117 testing, this regimen is asserted to inflict upon a coating all the stresses expected in northern climates.

6.4 CYCLIC/COMBINATION TESTS: New cyclic/com­bination exposure apparatuses have been developed by the automotive industry which put panels through complex multi-step cycles with light, controlled humidity, humidity with condensation, and electrolyte exposure.

6.4.1 Cyclic Immersion with Exposure to Light and Heat: Recently, a cabinet test was submitted to ASTM for consideration which entails an immersion cycle in an electrolyte of the testerʼs choosing along with humidity and UV exposure. The method was devised to test performance of industrial maintenance coatings. This multi-component cyclic immersion test is currently being evaluated by both ASTM and SSPC.

6.5 IMMERSION TESTING: The procedures described in ASTM D 870 include either partial or full immersion in dis­tilled or de-mineralized water at atmospheric pressure. The temperature and the duration of the test can vary. Ratings are based on blistering, color change, loss of adhesion, softening, or embrittlement.

6.6 INFLUENCE OF COATING CHARACTERISTICS ON ACCELERATED TESTING: The results from accelerated tests depend on the behavior of the coating film under the stresses imposed by the test protocol. This behavior is related to funda­mental characteristics of the coating system. Length of exposure for any test method discussed in this document depends on the types of coatings being tested, the expected outcome of the experiment, and other experimental design factors. The lengths of exposure referenced in this document are not intended to indicate minimum or maximum duration of expsoure for any of the methods referenced in this document.

6.6.1 Coating Thickness
6.6.1.1 Permeability: In many accelerated corrosion tests the coating system is subjected to high humidity or direct contact with water. The permeability of the coating film will influence the degree to which water transports to the substrate. In gen­eral, a thicker film coating system will have slower transport of water to the substrate.

6.6.1.2 Cracking Resistance: Another example of system behavior influenced by film thickness is cracking resistance. Particularly in freeze-thaw exposures, overly thick films may show a greater tendency to crack.

6.6.2 Pigmentation: The type of pigmentation present in a coating film influences the behavior of that system in real exposures. This also holds true for the behavior of the coating system under certain accelerated tests, though the behavior exhibited may not be that found in nature. For instance, in salt fog exposure (ASTM B 117), an anti-corrosive pigment may rapidly deplete from a primer. Conversely, under the same exposure conditions, a zinc-rich inorganic primer will show high resistance to rusting. In part this is because the zinc metal pigment forms a reaction product with the salt that serves to seal pores in the coating.

By way of contrast, in cyclic salt fog exposure in accor­dance with ASTM G 85 – Appendix 5, untopcoated zinc-rich primers show surprisingly poor performance. The reaction product of the zinc in this experiment is soluble and washes from the surface. Thus, the zinc-rich primer never seals and will show early corrosion. This behavior is unlike that found in normal atmospheric performance. As a result, ASTM G 85 -Appendix 5 cyclic salt spray is not recommended for use in evaluating untopcoated zinc-rich primers.

6.6.2.1 Barrier Pigments: Barrier pigments can influence behavior in accelerated tests in several ways. Barrier pigments such as aluminum flake or micaceous iron oxide improve per­meability resistance to water; they may also serve to improve chalking resistance. Flexibility and cracking resistance are also modified or enhanced in a coating material which incorporates barrier pigmentation.

6.6.2.2 Color Pigments: For a given proprietary product, different pigment blends may be used to achieve a particular color. As a result, different colors of the “same” coating may exhibit different performance characteristics (permeability, gloss and color retention, etc.) in accelerated tests.

6.6.3 Resin Type: The type of resin will play a role in coat­ing system behavior in accelerated testing. Examples include high resistance to chalking by acrylics and urethanes when exposed to ultraviolet light, and saponification of alkyd resins in salt fog (ASTM B 117) exposure. Degree of permeability is also directly related to resin type and coating chemistry. For example, alkyds are more permeable than epoxies; and depending on formulation, one epoxy can be more permeable than another epoxy.

7. Disclaimer
7.1 This technology update is for information purposes only. It is neither a standard nor a recommended practice. While every precaution is taken to ensure that all informa­tion furnished in SSPC technology updates is as accurate, complete, and useful as possible, SSPC cannot assume responsibility nor incur any obligation resulting from the use of any materials, coatings, or methods specified herein, or of the technology update itself.

7.2 This technology update does not attempt to address problems concerning safety associated with its use. The user of this specification, as well as the user of all products or prac­tices described herein, is responsible for instituting appropriate health and safety practices and for ensuring compliance with all governmental regulations.

8. References

1.     Performance of Alternate Coatings in the Environment, SSPC reports 89-03, 89-11, 89-12 (1989).

2.     A. F. Sherwood, The Protection of Steel Work Against Atmospheric Pollution: Part II – Natural Weathering and Laboratory Tests, Paint Research Association Technical Report 8-87, December 1987.

3.     B. R. Appleman, “Survey of Accelerated Test Methods for Anti-Corrosion Coating Performance,” Journal of Coating Technology, 62, 787 (1990): p. 57.

4.     F. D. Timmins, “Avoiding Paint Failures by Prohesion,” Journal of the Oil and Colour Chemists Association, 62, 4 (1979): p. 131.

5.     C. H. Simpson, C.J. Ray, B.S. Skerry, “Accelerated Corrosion Testing of Industrial Maintenance Paints Using a Cyclic Corrosion Weathering Method,”Journal of Protective Coatings and Linings, 8, 5 (1991): p. 28.

6.     Performance Testing of Marine Coatings, SSPC report 90-02 (1990).

7.     M. E. McKnight, J. D. Martin, “Quantitative Evalua­tion of Blistering and Corrosion in Organic Coating Systems,” in New Concepts for Coating Protection of Steel Structures, ASTM STP-841 (1984), p. 13.

8.     Advances in Accelerated Testing and Coating Characteristics, SSPC 91-15 (1991).

APPENDIX A SSPC ENVIRONMENTAL ZONES
0	Dry interiors where structural steel is imbedded in concrete, encased in masonry or protected by membrane or non-corrosive contact type fireproofing.
1A	Interior, normally dry (or temporary protection). Very mild (oil base paints now last six years or more).
1B	Exteriors, normally dry (includes most areas where oil base paints now last six years or more).
2A	Frequently wet by fresh water. Involves condensation, splash, spray or frequent immersion. (Oil base paints now last five years or less.)
2B	Frequently wet by salt water. Involves condensation, splash, spray, or frequent immersion. (Oil base paints now last three years or less.)
2C	Fresh water immersion
2D	Salt water immersion
3A	Chemical atmospheric exposure, acidic (pH 2.0 to 5.0)
3B	Chemical atmospheric exposure, neutral (pH 5.0 to 10.0)
3C	Chemical atmospheric exposure, alkaline (pH 10.0 to 12.0)
3D	Chemical atmospheric exposure, presence of mild solvents. Intermittent contact with aliphatic hydrocarbons (mineral spirits, lower alcohols, glycols, etc.)
3E	Chemical atmospheric exposure, severe. Includes oxidizing chemicals, strong solvents, extreme pH’s or combina­tions of these with high temperatures.

APPENDIX B Characteristics of Common Accelerated Test Methods
		STRESS APPLIED

TEST METHOD	Heat	Salt	Humidity	Light	CYCLIC	STANDARD	COMMENTS
Salt Fog	Yes	Yes	Yes	No	Constant	ASTM B 117	Developed to mimic marine exposure
Humidity Testing	Yes	No	Yes	No	Constant	ASTM D 2247	Test water resistance
Humidity Testing	Yes	No	Yes	No	Constant	ASTM D 4585	Includes drying period using dry forced air
Light/Condensation	Yes	No	Yes	Yes	Cyclic	ASTM D 4587, ASTM G 153	Care in selection of UV bulbs
						ASTM G 23,
Artificial Weathering	Yes	No	Yes	Yes	Cyclic	Carbon Arc; ASTM G 26,	Shielding if light source required
						Xenon Arc
Weathering	—­	—­	—­	—­	—­	ASTM G 26, Xenon Arc	Shielding if light source required
SO 2/Moisture Exposure	Yes	Yes	Yes	No	Cyclic	ASTM G 87	Intended for testing of coil coatings, alloys
Immersion Testing	Yes, Optional	No	No	No	Constant	ASTM D 870
Immersion, Chemical	Yes, Optional	Chemical Exposure	Yes, Above Fluid Line	No	Constant	ASTM D 868, NACE TM 0174	Testing of linings
High Temperature/High Pressure Immersion	Yes, Optional	Yes, Optional	No	No	Constant	Proposed Standard	Accelerates blistering failure, used by marine
Cyclic Salt Spray	Yes	Yes	Yes	No	Cyclic	ASTM G 85	Forced air drying of coatings, constant temperature
Cathodic	No	Yes	No	No	Constant	ASTM G 8
							Uses special weak salt
Cyclic Salt Spray	Yes	Yes	Yes	No	Cyclic	ASTM G 85, Appendix A5	solution, drying of panels by heating of chamber and passage of dry air; salt fog at
							25OC, drying at 35OC
Combined Cyclic Salt
Spray and UV/	Yes	Yes	Yes	Yes	Cyclic	ASTM D 5894
Condensation
Freeze-Thaw Humidity	Yes	No	Yes	No	Cyclic	ASTM D 2246	Used in conjunction with UV exposure as an option
Freeze-Thaw, Salt Fog, Humidity Testing	Yes	Yes	Yes	No	Cyclic	None
Light, Immersion, Humidity Exposure “Envirotest”	Yes	Yes, Optional	Yes	Yes	Cyclic with Immersion	Standard in Preparation
Accelerated Outdoor	Yes	No	Ambient	Yes	Natural cycle	ASTM D 4141
Accelerated Outdoor	Yes	Yes	Ambient	Yes	Natural Cycle	None	Panels sprayed with salt or acid solution at regular intervals

TECHNOLOGY UPDATE NO. 05 – Accelerated Testing of Industrial Protective Coatings