Galvanized elbow

Galvanized elbows are a type of elbow with a layer of zinc coated on their surface to enhance their corrosion resistance. There are two categories of galvanized elbows: hot-dip galvanized and electro-galvanized. Hot-dip galvanized elbows have a thick zinc coating, while electro-galvanized elbows feature low cost and a relatively rough surface finish.

### Galvanized Elbow Production Processes

1. Optimization of Sulfate Galvanizing

The greatest advantage of sulfate galvanizing for elbows is its current efficiency of up to 100% and fast deposition rate, which is unmatched by other galvanizing processes. Due to the relatively coarse coating crystals and poor throwing power and covering power, this process is only suitable for electroplating geometrically simple pipes and wires.

2. Transformation of Sulfate Galvanizing

For sulfate electro-galvanized elbow iron alloys, only zinc sulfate—the main salt of sulfate galvanizing—is retained. Other components such as aluminum sulfate and alum (potassium aluminum sulfate) can be removed by adding sodium hydroxide during plating solution treatment to form insoluble hydroxide precipitates. Organic additives are removed by adsorption with powdered activated carbon.

3. High Deposition Rate and Excellent Protective Performance

The sulfate electro-galvanized elbow alloy process achieves a current efficiency of 100% and an unrivaled fast deposition rate among all galvanizing methods. Fine tubes operate at a speed of 8 to 12 meters per minute, with an average coating thickness of 2 micrometers per minute—an effect difficult to achieve with continuous galvanizing.

4. Unique Clean Production

Galvanized elbows produced via the sulfate electro-galvanized iron alloy process feature through-holes between production line tanks, ensuring no solution carryover or overflow.

5. Special Characteristics of Electroplating Equipment

Electroplating for galvanized elbows, like wire electroplating, belongs to continuous electroplating but uses different plating equipment. The plating tank for iron wire is designed for its long, slender shape—long, wide, and shallow. During electroplating, iron wire passes through holes and spreads linearly on the liquid surface while maintaining spacing between strands.

### Applications of Galvanized Elbows

Galvanized elbows are commonly used for connecting iron pipes in gas and heating systems. When used as water pipe connectors, however, they develop heavy rust scale after several years of service. The yellow rusty water not only stains sanitary ware but also carries bacteria growing on the rough inner walls. Corrosion leads to excessive heavy metal content in water, posing a serious health risk to humans.

In the 1960s and 1970s, developed countries began developing new pipe materials and gradually phased out galvanized pipes and galvanized elbows. Four ministries including the Ministry of Construction of China also issued a document explicitly banning galvanized elbows starting in 2000. At present, galvanized elbows are rarely used for connecting cold water pipes in newly built residential areas, though some communities still use them for hot water pipe connections.