... painted black or as per customers' requestCertificatesGB3091-2001, ASTM A53, ASTM A106 EN10216,EN10219Manufacture Technique high frequency welded Packaging in ... metallurgy ,papermaking ,chemical,medical equipment ,aviation ,boiler heat, exchanger,shipbuilding,construction,etc addition: 1.Special design available accorting to ... your own request to the supplier. big diameters ASTM A213 T23 steel pipe