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How to deal with the rust problem in the fabrication of automotive sheet metal parts?

It has to be admitted that rust water often seeps out after the phosphating treatment of automobile sheet metal parts, which is a difficult problem for many sheet metal fabrication plants. So how to avoid rust and deal with this problem? First, people need to find the reasons for this situation to carry out analysis.

  • 1. During pickling and passivation, the acid in the gap is not neutralized or not completely neutralized, and the acid pickling and phosphating is not complete and easy to rust. After spraying, the rust will spread and overflow into the gap after a period of time.
  • 2. Passivation by strong alkali pickling and degreasing by strong partial alkali. After the drugs remaining in the crevices are neutralized by oxidation, many manufacturers have not cleaned them with tap water, which results in milky white formation on the crevices after drying. After spraying for a period of time, this milky white product and the corrosive substances in the gas cause some kind of exothermic reaction in the overflow gap. This problem mostly occurs between March and December.

The solution to people’s sheet metal fabrication to avoid corrosion problems is the following:

  • 1. Deoiling must use weak partial alkali deoiling, must not contain flake alkali, TAL should be controlled at around 15POINT, and PH should not exceed 12.
  • 2. For the process of pickling and passivation, hydrochloric acid can be used for pickling and passivation. The time of pickling and passivation is good and it does not need to be too long. It is just right to use ammonium sulfate.
  • 3. After pickling and passivation, please use 1~2 sodium carbonate to neutralize.
  • 4 Surface adjustment is best to use organic chemicals such as hydrochloric acid, and the concentration value of 1~2 degrees can be used.
  • 5. The phosphating acid value of zinc-based pickling should be limited, and the pre-dipping solution should be tried: TA: about 45, FA: 1.3AC: 8 (20cc hair alcohol tube).
  • 6. All hand-washing projects must not be cleaned and tidy, and hand-washing should maintain overflow.
Automotive Sheet Metal Fabrication

Pintejin Sheet Metal shop offers a cost-effective solution for a wide range of industries with our custom metal stamping and custom sheet metal fabrication capabilities. Our stampnig operations include a variety of sheet-metal forming manufacturing processes, such as punching, blanking, embossing, bending, flanging, and coining. Our professional, experienced and well-trained engineers can execute the complex metal stamping operations with precision and accuracy.

No matter what your metal fabrication needs are, Pintejin can offer the right solution: from single sheet metal part or sub-assembly of stamped metal parts to turnkey solutions for mechanical and electrical assemblies. We have the technology, equipment and the experience to fabricate customised metal products from aluminium sheet metal fabrication, steel, zinc plated steel, stainless steel sheet metal fabrication, brass and copper. Designs that require CNC machining of surfaces or components can be accommodated. We can supply polished, galvanized, zinc coated or powder coated finishes for any sheet metal work or stamped metal components. Coupled with our accurate and reliable metal fabricating equipment, we guarantee precision and repeatability in custom sheet metal work. You’ll be taking advantage of the best sheet metal fabrication china can produce.


With Pintejin automated and highly streamlined sheet metal fabrication service, you can expect a sheet metal fabrication quote within 12 hours and lead times as quickly as three days.Our rapid prototyping offering also includes a solid and reliable manufacturing capability (led by our expert team with 15+ years of experience) and technical and quality assurance, including SGS and RoHS material certifications, in-process quality reports, and First Article Inspection.



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