Ø21 (Phi 21) Steel Pipes: Types, Pros & Cons, andApplications
Sắt Thép Lộc Thiên currently supplies two main Ø21 (phi 21 /D21) steel pipe lines: black steel pipes and galvanized steel pipes. Eachoption differs in protective coating, durability in various environments,aesthetics, and where it fits best in construction and mechanical uses.
1) Ø21 Black Steel Pipes
Advantages
High rigidity and excellent load‑bearing capacity, ideal forframes and steel structures.
Resists deformation under heavy loads or strong impacts.
Wide range of specifications, suitable for many types ofprojects.
Competitive price, lower than galvanized steel pipes.
Disadvantages
No protective coating, so corrosion resistance is lower thangalvanized pipes.
Hot‑rolled black surface—less aesthetic for projects thatrequire a bright, clean appearance.
Typical applications
Frames, scaffolding, factory frameworks.
Vehicle frames, internal piping, and mechanical components.
2) Ø21 Galvanized Steel Pipes
Advantages
Black steel pipes with an additional hot‑dip or electro‑galvanizedcoating for optimal rust protection.
Suitable for humid, outdoor, or coastal environments.
Varied sizes, convenient for water supply/drainage and fireprotection systems.
Bright, clean surface for better aesthetics.
Long service life, reducing maintenance costs versusstandard steel pipes.
Disadvantages
Higher price due to the protective zinc layer.
Typical applications
Water supply and drainage, fire protection (PCCC), and otheroutdoor civil/industrial uses.
Note: Besides the two options above, Ø21 seamless steelpipes are often chosen for high‑pressure and high‑temperature applications suchas oil lines, steam lines, or stringent fire protection (PCCC) systems.
3) Common Applications of Ø21 Steel Pipes
Construction
Scaffolding, frames, and structural supports.
Railings, fences, stair components.
Industrial & domestic piping
Clean water and wastewater lines.
Air and compressed‑air lines.
Oil, steam, and other industrial fluids (especially suitablefor seamless pipes).
Mechanical & furniture
Frames for tables, chairs, beds, and shelving.
Electrical & telecommunications
Conduits for electrical wiring and fiber‑optic cables; usedacross MEP systems.
Fire protection
Steel pipes—particularly seamless—are widely used in fireprotection (PCCC) installations.
4) Which should you choose: black or galvanized?
Prioritizing cost and using in dry, indoor environments:choose Ø21 black steel pipes.
Needing long‑term durability and corrosion resistance, usedoutdoors or in humid/saline areas: choose Ø21 galvanized steel pipes.
Before ordering, define the operating environment, technicalrequirements, specifications & wall thickness, and relevant standards tooptimize both cost and service life.
5) Trusted Supplier of Ø21 Steel Pipes
Sắt Thép Lộc Thiên distributes high‑quality steel pipes fromreputable brands such as Hòa Phát, Hoa Sen, SeAH, and more—serving projectsfrom small jobs to large‑scale developments.
Your benefits when buying from Sắt Thép Lộc Thiên
Products certified with CO–CQ, with clear origin.
Free shipping in many areas.
Attractive discounts for bulk orders.
Referral commissions for customers who introduce new buyers.
Flexible payment options.
Fabrication and cut‑to‑size service for Ø21 pipes uponrequest.
6) Contact Sắt Thép Lộc Thiên
Address: Số 1001, tổ 22, KP1, P. Long Hưng, TP. Biên Hòa, ĐồngNai
Fanpage: https://www.facebook.com/sattheplocthien
Email: sattheplocthien@sattheplocthien.com
Hotline: 0858 676 679
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Website: https://sattheplocthien.com/
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