P R O D U C T D A T A B U L L E T I N Aluminized Steel Type 1 STAINLESS and Excellent Resistance to Pitting Corrosion from Road Salt Excellent Resistance to Muffler Condensate Corrosion Red Rust Protection to 8ºF (427ºC) Oxidation Resistance to 155ºF (843ºC) (Aluminized ) and 17ºF (927ºC) (Aluminized ) Excellent Formability for Exhaust System Components Easier to Post-paint or Coil-coat than Uncoated Stainless AK Steel s Aluminized and Stainless Steel products have been developed to provide the automotive industry with life-of-the-car exhaust system materials. The Type1 hot dip aluminum coating provides excellent resistance to pitting from muffler condensate and road salt, allowing the exhaust system to resist internal chlorides and retain good external appearance, even at uncoated welds. The aluminum coating significantly extends the life of the exhaust system over that of bare stainless. ALUM---B-1--1
External Exhaust Salt-Humidity Pitting Corrosion At relatively low temperatures (e.g. 6 F [316 C]), forms a heat tinted (oxidized) surface and pits readily after exposure to moist salt. The hot dip aluminum coating provides long term galvanic protection against pitting corrosion. Uncoated is only slightly affected by pitting after 6 F (316 C) exposure, but will form surface red rust due to heat tinting. Aluminized provides long term protection against cosmetic red rusting. Figure 3 Muffler Simulation 6ºF (316 C) HEAT TREAT - BOLD EXPOSURE PIT DEPTH, (INCHES).4.3.2.1 AL 2 4 6 8 1 12 After 8 F (427 C) heat treatment, the four materials tested all show at least double the pitting rates compared to 6 F (316 C). However, the effects of increased heat tint are much greater for uncoated. Test cycle: Sample - 4" by 6" (12mm by 152mm) formed Heat 1 hour in air once per week Daily dip 15 min - 5% NaCl Air dry (75 min.) Humidity cabinet - 85% RH, 14 F (6 C) (remainder of day) Figure 4 I-Pipe Simulation 8ºF (427 C) HEAT TREAT - BOLD EXPOSURE PIT DEPTH, (INCHES).5.4.3.2.1 2 4 6 8 1 12 AL 3
External Exhaust Salt-Humidity Pitting Corrosion (continued) A 1 F (538 C) heat treat in the corrosion cycle test fully alloys the aluminum coating with the stainless steel substrate. The lower galvanic potential of the thick alloy coating provides longer term protection against pit initiation. The effects of oxidation plus salt on the higher chromium uncoated grades cause earlier perforation compared to lower temperature testing. In Figure 5, bare shows a shelf in pitting rate and eventually exhibits large weight loss due to development of a loose scale jacket. A thinner walled AL product can result in improved catalytic converter life and reduced weight compared to bare. Field corrosion data indicate that the 1 F (538 C) test equivalence is approximately 1 week = 1 year in severe salt climate service. At lower test temperatures the indicated equivalence is more than 1 year. Because of very rapid pitting rates after 14 F (76 C) heat treat, the measurement is switched to weight loss. All bare stainless grades tested exhibit similar behavior, while the coated grades continue to benefit from extended galvanic protection by the fully alloyed coating. Salt corrosion of this type is generally associated with salt held on a pipe by insulation or shielding. Figure 5 Converter Simulation 1ºF (538 C) HEAT TREAT - BOLD EXPOSURE PIT DEPTH, (INCHES) Figure 6.5.4.3.2.1 AL 2 4 6 8 1 12 Front Pipe Simulation 14ºF (76 C) HEAT TREAT - BOLD EXPOSURE CORROSION RATE; mils/year 4 3 2 1 5 T34 11 Cr-Cb 18SR T 18 Cr-Cb AL 3 5 4
Muffler Condensate Corrosion Aluminized Steel Type and Type are highly resistant to acid condensate pitting. The aluminum coating provides protection against the start of pitting for much of the vehicle life. It galvanically protects against initial converter chloride corrosion at very low ph levels. This protection can be even further extended by avoiding dissimilar material contacts. Figure 7 shows pitting rates in a synthetic condensate boil-down test. Daily Test Cycle: - Partially immerse flat sample in synthetic condensate* and slowly evaporate to dryness at 194 F (9 C) - approx. 12 16 hours - When dry, heat sample to 482 F (25 C) for 1 hour - Humidity cabinet at 122 F (5 C) 85% RH - approx. 6 hours *Synthetic Condensate: Ammonium salts of Cl - (1ppm); NO 3 (1ppm); CO 3 (3ppm); SO=(5ppm); initial ph=8.5 Mechanical Properties Typical mechanical properties for Aluminized Steel Type 1 Stainless are shown in Table 1. See Table 2 for Aluminized Steel Type 1 Stainless. Figure 7 Boiling Beaker Cycle Test for Muffler CONDENSATE CORROSION PIT DEPTH, ((INCHES) Table 1.2.16.12.8.4 Mechanical Properties ALUMINIZED AL 5 1 15 2 25 3 35 4 NO. CYCLES (DAYS) 34 436S Avg. Sheet Thickness.2% YS UTS % Elong. (Nom.) ksi MPa ksi MPa in 2" (51mm).22" to under.3" (.56mm to under.76mm) 43 297 65 448 26 >.3" (.76mm) 38 262 6 414 32 Table 2 Mechanical Properties ALUMINIZED Avg. Sheet Thickness.2% YS UTS % Elong. (Nom.) ksi MPa ksi MPa in 2" (51mm).22" to under.3" (.56mm to under.76mm) 48 331 73 54 26 >.3" (.76mm) 43 297 68 469 32 5
AK STEEL ALUMINIZED STEEL TYPE 1 STAINLESS AND Weldability High Frequency AK Steel and Aluminized Type 1 Stainless Steels are welded using established techniques for uncoated stainless and aluminized carbon steels. Laser successfully applied to exhaust tubing and seam welds. Spot and Resistance Seam Techniques are similar to those for other aluminized steels, and the weld structure will be similar to that of uncoated Type or Type SS. GMAW Filler wires recommended are 1) Ti, 2) 18 Cr-Cb, 3) 38L and 4) Cb ( only). GTAW Not recommended without sufficient filler wire to avoid excess aluminum in the weld. Carbon steel or lower chromium wire should be avoided because of lower oxidation resistance and sacrificial corrosion due to galvanic coupling with Type or Type. More Information / Technical Assistance AK Steel s Technical Representatives can provide you with more detailed information concerning these products. They also are available to assist you in solving any welding, forming, painting or other material selection issue. Outside Processing Tailored blanks, tension leveling, resquaring, slitting, cuttingto-length, and coil coating are some of the services AK Steel can provide through arrangements with outside processors. Mill Limits Aluminized Steel Type 1 Stainless and are generally available in thicknesses from.18" (.46mm) to.8" (2.3mm), and widths up to 48" (1219mm) depending on thickness. For sizes outside these limits, please inquire. The information and data in this bulletin are accurate to the best of our knowledge and belief, but are intended for general information only. Applications suggested for the materials are described only to help readers make their own evaluations and decisions, and are neither guarantees, nor to be construed as express or implied warranties of suitability for these or other applications. Data referring to mechanical and corrosion properties and chemical analyses are the result of tests performed on specimens obtained from specific locations of the products in accordance with prescribed sampling procedures; any warranty thereof is limited to the values obtained at such locations and by such procedures. There is no warranty with respect to values of the materials at other locations. AK Steel and the AK Steel logo are registered trademarks of AK Steel Corporation. SPECIALTY AND STAINLESS STEEL FIELD SALES OFFICES AK Steel Corporation 73 Curtis Street Middletown, OH 4543-1 Butler Works P.O. Box 169 Butler, PA 163-169 Customer Service... 8-381-5663 www.aksteel.com AK Steel Sales Offices Atlanta, GA-Southeast Region... 77-514-23 Baltimore, MD... 41-612-1338 Charlotte, NC... 74-662-786 Chicago, IL-West Central Region... 63-368-1 Cincinnati, OH- Mideast Region... 513-683-53 Detroit, MI-North Central Region... 248-641-7595 Grand Rapids, MI... 616-949-5278 Nashville, TN-Southwest Region... 615-771-3134 New England... 41-658-3468 Pittsburgh, PA... 412-635-9835 Tulsa, OK... 918-298-2272 International Sales-Houston, TX... 281-872-8741 Specialty Stainless and Electrical Commercial-Butler, PA... 8-381-5663 21 AK Steel Corporation PD-SS ALUM 425-67 1/1