• Completing solution manufacturing technology of environmentally friendly passive solutions without hexavalent chromium ions for zinc coatings. Three type of passive solutions are made (02 iridescent type and 01 white-blue type).

• Production scale and product demand:
  • Production scale: 60.000 – 100.000 liters/year
  • Product demand: 500.000 liters/year

On science results:

• Have studied to perfect the white-blue passive solution (B) in which 0.2 – 0.3 g/l malonic acid was added to reduce the passive time and increase the uniformity of samples. Have studied to perfect the iridescent passive solution by increasing NaNO₃ to solve problems when making new solution bath.

• Have studied to fabricate successfully the second iridescent passive solution (C₂) with two complex formation agents are oxalic and succinic acid.

• Have studied preliminarily method for recovering Cr from industrial Ni-Cr plating residues. The results show that passive solution can make from residues. However, this is only the initial results and to be able to apply to production researches need to continue to develop it further.

• Have completed technological process and production line to produce all types of passive solutions. Have proposed technological process to produce passive solution with inputs as CrO₃. This is reserve process in the absence of material Cr(III).

• Have developed the process of checking the quality of inputs, quality of product, basic standards and procedures management records.

• In addition, the project has also completed the following criteria:
  • Publication: 03 paper
  • Training: 01 PhD, 01 master
  • Intellectual property: applied to register intellectual property and application has been accepted valid.

On production & testing results: Have produced 21,600 liters of passive solutions (3 types as registered) with satisfactory quality and 2,500 liters of white-blue passive solution without salt spray.

Co. Mechanical Quang Manh, Surface Technology Joint stock company.

In the content of the project, the problem of sludge treatment of Ni-Cr plating industry for recovery has been made and there are some positive results. However, these are only preliminary results and insufficient grounds to put into practice. To be able to put into production, we see the need to continue to solve the following issues:

• Due to Ni-Cr plating industrial sludge is a very complex system, further research should be carried out to be able to find optimal solutions and technological stability.
• In the project, research on sludge of only Goshi Thang Long plant is conducted. It should be extended to the sludge of other plants, in order to find out the appropriate processes for different types of sludge.
• In the project, research on sludge is conducted only in laboratory scale. It is necessary to conduct a larger scale in order to improve the process.
• Apart from the recovery of Cr to produce passive solution, the recovery of Cr for other purposes such as industrial pigments, Cr in the form of Cr(VI) and Ni has not been done in project. Ni can be recovered to produce Ni salts or Ni metal. The recovery of all metals in the sludge will indeed bring economic benefits and contribute to reducing emissions and protecting the environment.

Therefore, we expect to continue to implement another project in this direction and look forward to the support of the Vietnam Academy of Science and Technology and the Institute for Tropical Technology.