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1 mesh size: SAE G-25 to SAE G-40 <br /> 2 <br /> 3 3. Garnet, flint, or crushed nickel or black beauty coal slag <br /> 4 mesh size: SAE G-25 to SAE G-50 <br /> 5 <br /> 6 Where zinc coatings greater than 0.010 inch thick are to be applied, one of the <br /> 7 following abrasive grits shall be used with pressure blast equipment to produce a <br /> 8 5.0 mils AA anchor tooth pattern: <br /> 9 <br /> 10 1. Aluminum oxide or silicon carbide <br /> 11 mesh size: SAE G-18 to SAE G-25 <br /> 12 <br /> 13 2. Hardened steel grit <br /> 14 mesh size: SAE G-18 to SAE G-25 <br /> 15 <br /> 16 3. Garnet, flint, or crushed nickel or black beauty coal slag <br /> 17 mesh size: SAE G-18 to SAE G-25 <br /> 18 <br /> 19 The pressure of the blast nozzle, as measured with a needle probe gauge, with <br /> 20 pressure type blasting equipment shall be as follows: <br /> 21 <br /> 22 1. With aluminum oxide, silicon carbide, flint, or slag - 50 psi minimum and 60 <br /> 23 psi maximum. <br /> 24 <br /> 25 2. With garnet or steel grit - 75 psi minimum. <br /> 26 <br /> 27 The pressure at the blast nozzle, with siphon blasting (suction blasting), shall be as <br /> 28 follows: <br /> 29 <br /> 30 1. With aluminum oxide, silicon carbide, flint, or slag - 75 psi maximum. <br /> 31 <br /> 32 2. With garnet or steel grit- 90 psi maximum. 111 <br /> 33 <br /> 34 The abrasive blast stream shall be directed onto the substrate surface at a spray <br /> 35 angle of 75 to 90 degrees, and moved side to side. The nozzle to substrate <br /> 36 distance shall be 4 to 12 inches. <br /> 37 <br /> 38 6-07.3(14)F Application of Metallic Coating <br /> 39 No surface shall be sprayed which shows any sign of condensed moisture or which <br /> 40 does not comply with Section 6-07.3(14)E. If rust bloom occurs within the holding <br /> 41 time between abrasive blast cleaning and thermal spraying, the surface shall be <br /> 42 reblasted at a blast angle as close to perpendicular to the surface as possible to <br /> 43 achieve a 2.0 to 4.0 mil anchor tooth pattern. Thermal spraying shall not take place <br /> 44 when the relative humidity is 90% or greater, when the steel temperature is less <br /> 45 than 5°F above the dew point, or when the air or steel temperature is less than <br /> 46 40°F. <br /> 47 <br /> 48 Clean, dry air shall be used with not less than 50 psi air pressure at the air <br /> 49 regulator. Not more than 50 feet of 3/8 in. ID hose shall be used between the air <br /> 50 regulator and the metallizing gun. The metallizing gun shall be started and <br /> 51 adjusted with the spray directed away from the work. During the spraying operation <br /> 52 and depending upon the equipment being used, the gun shall be held as close to <br /> I <br /> AMENDMENTS TO THE 2014 STANDARD SPECIFICATIONS BOOK <br /> Revised: 8/3/15 <br />