Black vs Galvanized Malleable Iron Pipe Fittings
PT Tri Sinar Purnama manufactures malleable iron pipe fittings in two finishes: black and hot-dip galvanized. The finish determines whether a zinc coating is applied to the casting. It is selected alongside — not instead of — the applicable design standard, thread system, size and pressure–temperature requirement for the job. Both finishes are produced on TSP’s own sites in Semarang, in sizes from ¼″ to 6″.
What are black malleable iron fittings?
A black fitting is a malleable iron pipe fitting supplied without the hot-dip zinc coating. It is cast, annealed, ground, shot blasted, threaded and machined on the same production route as a galvanized fitting; the galvanizing stage is simply not applied.
On TSP product documentation, finish appears as its own attribute — Zinc Coating: Galvanized / Black — separate from the product’s design standard, thread standard and size range.
What are galvanized malleable iron fittings?
A galvanized TSP fitting is the same malleable iron casting with a hot-dip zinc coating applied. In TSP’s production sequence, galvanizing is stage 10 of 16: it follows shot blasting (stage 09) and precedes tapping (stage 11), so the threads are cut after the casting has been coated.
The zinc-coating requirement that applies to a given fitting is set by its standard family, not by the finish alone:
| Standard family | Zinc coating reference |
|---|---|
| American | ASTM A153 |
| European | EN 10242 |
| British | BS 143 & 1256 |
| Japanese | JIS B 2301 |
Black vs galvanized: factual comparison
The table compares only attributes that TSP can support from its own product, process and quality-control documentation.
| Attribute | Black | Hot-dip galvanized |
|---|---|---|
| Zinc coating applied | No | Yes — hot dip |
| Base casting | Malleable iron, per the material specification of the applicable standard family | Identical — same casting, same material specification |
| TSP production route | Stages 01–09 and 11 onward | Same route, with stage 10 (galvanizing) applied |
| Coating-thickness inspection | Not applicable | TSP in-process check — Elcometer, 10 spots per sample, minimum 65 µm |
| Coating standard reference | Not applicable | Per applicable family: ASTM A153 / EN 10242 / BS 143 & 1256 / JIS B 2301 |
| Size range offered | ¼″ – 6″ | ¼″ – 6″ |
| Relationship to design & thread standard | Finish is recorded as a separate product attribute from design standard, thread standard and size on TSP product documentation. | |
How TSP manufactures the two finishes
Both finishes come off the same integrated production route in Semarang — pattern making, core making, moulding, melting and casting, annealing, grinding, shot blasting, tapping, machining and packing. Galvanizing is one stage inside that route, applied after shot blasting, with coating thickness verified using an Elcometer.
See the full 16-stage TSP production sequence and the equipment installed at each stage.
Quality control for galvanized fittings
Zinc coating thickness is one of the in-process checks TSP applies during production:
| Check | Method and acceptance criterion | Frequency |
|---|---|---|
| Zinc coating thickness | Elcometer, 10 spots per sample, minimum 65 µm | During process |
See all TSP in-process quality control checks, methods and acceptance criteria.
Standards and technical ratings
Finish does not replace the rest of the specification. A fitting is still defined by its design standard, thread standard, material specification, size and applicable pressure–temperature rating. No single standard listed by TSP applies to every TSP product.
View TSP thread and pressure–temperature reference data, or read the explanation of the American, European, British and Japanese standard families.
Selecting a finish for your specification
Confirm the required finish, standard, thread and size with TSP before specification or ordering. Where a project specification sets a coating requirement, that requirement governs.
Browse the TSP malleable iron pipe fitting range · Certifications and approvals · Request a specification
PT Tri Sinar Purnama is an Indonesian manufacturer of malleable iron pipe fittings, operating an integrated malleable iron foundry in Semarang, Central Java, established in 1983.