GB/T 23257 — 埋地钢质管道聚乙烯防腐层 GB/T 23257-2009 埋地钢质管道聚乙烯防腐层. CNAS-accredited laboratory test standard. Version reference only. No standard text. GB 1033.1 1462 13657 5169.16 5349 228.1 7690.3 GB 9274 1771 1452 5169.12 4618.2 Testing: info@leisa.com