Materials Performance Supplements

CORTEC 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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a number of laboratory studies as well as real-life application. Laboratory Testing: Humidity Testing ASTM D1735 3 and D1748 4 conditions are standard accelerated weathering envi- ronm ents. Both of th ese environm ents were used to evaluate the corrosion resis- tance of the oil film in non-submerged sit- uations such as the conditions experienced within an AST after a hydrotest and during preservation. astm d1735 ASTM D1735 is a test that examines a coating's resistance to constant water fog in a warm environment. The temperature of the chamber is held at 38 °C (100 °F), and deionized (DI) water is continuously fogged into this space such that 1.0 to 3.0 mL is collected on an 80 cm 2 surface area every hour. Steel panels are cleaned, coated with the f loat coat, and drained prior to being placed in the test chamber 15 degrees from vertical. Significant corro- sion is typically witnessed on control sam- ples within one day, but the duration of testing is dependent on how long the test panels remain free of corrosion. astm d1748 ASTM D1748 is a humidity test that examines a coating 's resistance to high temperature and humidity. The tempera- ture of the chamber is held at 48.9 ± 1.1 °C (120 ± 2 °F), and the panels are suspended by hangers designed so water does not drain from the hanger to the panel's sur- face. These hanging panels are then rotated through the chamber to allow every panel to experience identical conditions. Corro- sion is typically witnessed on control sam- ples within one hour, but the duration of testing is dependent on how long the test panels remain free of corrosion. This test was modified by using 0.063- by 2- by 4-in (1.6- by 51- by 102-mm) SAE 1008 cold- rolled steel panels and preparing the sur- face according to the procedure described in 8.2 through 8.3.6 without performing the heated solvent cleaning described in 8.3.7 through 9.2. Rather, the top edges of the panels were protected after removal from the solvent referenced in Section 8.3.6 and the f loat coat was applied to the panel as described in Section 9.2. Laboratory Testing: Immersion Testing Immersion testing was performed in a 3.5 wt% solution of sodium chloride (NaCl) in DI water. This solution was held in a cylindrical glass cell with a 5-in (127-mm) height and 2-in diameter. Two hundred grams of this solution were used in each test cell to ensure the full immersion of the tested steel panels (0.063- by 1- by 3-in [1.6- by 25- by 76-mm] SAE 1008 cold-rolled steel). Ten grams of pre- servative oil were added to each cell to build a substantially thick layer on the surface of the water. Pre-weighed steel panels were slowly lowered through the float coat into the test solution to ensure an even coating. These cells were placed into a 40 ± 2 °C oven for two weeks before being removed and left at ambient conditions (22 ± 2 °C) for 21 weeks. At this time the panels were removed, the oil residue was cleaned off with methanol, and oxides were cleaned from the surface via a 7.8 M hydrochloric acid (HCl) solution. The panels were examined for mass loss and the rate of corrosion was calculated using the fol- lowing formula from ASTM G31 5 (Equation 2, Section 12.4) shown in Equation (1): Corrosion Rate (mpy) = 3.45 × 106 × W A × T × D (1) where W represents the mass loss in grams, A is the panel surface area in cm 2 , T is the duration of the test in hours, and D is the metal density in grams per cubic centime- ter (7.87 g/cm 3 for SAE 1008 steel). The cor- rosion rate reduction was also calculated by comparing the control sample to the test samples, as shown in Equation (2): Corrosion Rate Reduction = 1– × 100% R C (2) where C represents the corrosion rate of the control sample and R is the corrosion rate of the test sample. Laboratory Testing: Coating Thickness and Dosing Estimation Coating thickness and appropriate dos- age were determined by constructing a ves- sel in which to simulate the float coating process. A 5-gal (19-L) container was fitted with a ball valve near its base to act as a drain while a rubber hose, guided to the base of the container via a 1-in diameter polyvinyl chloride pipe, was used to siphon water from another 5-gal container. Four- by twelve-in (102- by 305-mm) SAE 1008 steel panels were suspended in the center of the vessel to act as stationary steel surfaces would in an actual application. The proper dosage was deter- mined by considering the water surface area, monitoring the addition of oil until a consis- tent film formed on the water, and raising the water level to coat the suspended steel pan- els. When the coating applied evenly without breaking the oil surface as it was raised over the panel, the dosage was considered ade- quate for float coat application. After drain- ing the water from the vessel and allowing excess oil to drip from the test panel's sur- face, the film thickness was evaluated with a standard wet film thickness (WFT) gauge. Real World Analysis Float coating has been successfully used as an AST preservation method in the Middle East. This project provided afford- able c orrosion prot ection through th e application of a float coat while hydrotest- ing the system. The f loat coat was applied with neither minimal disruption to normal application procedures nor any negative impact on any cured phenolic epoxy liners, typically used in tanks. A water sample from the float coat sys- tem was submitted to a third-party chemical analysis firm for chemical testing. Analysis for several hazardous chemicals was per- formed, including dissolved metals, such as lead, mercury, and zinc, and several hazard- ous hydrocarbons, such as benzene, toluene, naphthalene, and others. Tests were carried out according to APHA 3120 B, 6 U.S. EPA SW 846/8260B, 7 and U.S. EPA SW 846/8081B 8 for various metals, volatile organic compounds, and organochlorine pesticides, respectively. Upon gaining disposal approval, hydrotest water was disposed of with minimal impact to normal operational procedures. Results Laboratory Testing: Humidity Testing astm d1735 Product A was tested according to ASTM D1735 to assess its corrosion protec- 11 CORTEC SUPPLEMENT TO MP MATERIALS PERFORMANCE JUNE 2017

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