PreCoat Z31, conversion coating for HDG

AD Chemicals metal surface treatment logo
  • Chromium-6 free;
  • Excellent adhesion, corrosion protection and cost effective processing
  • Meets the GSB and Qualisteelcoat standards, Qualicoat certified
  • Multi-metal application

PreCoat Z31 is a chromium(VI)-free pre-treatment for hot dip galvanized steel that has to be pretreated prior to the coating process, the so called DUPLEX coating. PreCoat is a multi-metal product that can also be used for aluminum. PreCoat Z31 Conversion coating for HDG enables perfect paint adhesion and corrosion protection. It also gives a protection against white rust (passivation layer) on the bare substrate.

PreCoat Z31 chromefree pretreatment hdg


Contact us for more information

+31 (0) 167 526 900

Chromium(VI)- free pretreatment of galvanized steel

PreCoat Z31 is developed for the needs of galvanizers that also offer a powdercoating or wet-painting service to their customers. PreCoat Z31 is a complete chromium(VI)-free pretreatment system (including etching, cleaning, conversion coating) .

PreCoat Z31 product characteristics:

  • Chromium(III) based
  • Spray, dip or cascade application
  • Free of substances of very high concern (SVHC
  • Multi-metal, suitable for all zinc and aluminum based alloys
  • Meeting the performance requirements of GSB and Qualisteelcoat
  • Qualicoat approved
  • Superior corrosion protection (up to 2000 hours salt spray testing)
  • Excellent paint adhesion

Customer case: Weert Groep (Netherlands)

AD Chemicals and Weert Group are introducing an innovative chromium (VI)- free pretreatment system prior to powder coating on galvanized steel (Duplex-system). Weert Group is the first galvanizer in Europe to implement this new technology that complies with both the GSB and Qualicoat (Approval No. A-119) standard.
For making this innovation possible, there has been a joint research and development trajectory of more than 8 years. The uniqueness of the PreCoat Z31 pretreatment lies in the fact that it is a 1-on-1 replacement for chromium (VI), meaning that all the qualitative properties are sustained (corrosion protection, paint adhesion, passivation). This results in a corrosion protection and paint adhesion of more than 2000 hours of NSS, a performance to be proud of. The expectation of AD Chemicals and Weert Group is that this new system will become the (global) market standard in chromium (VI) free pretreatments on galvanized steel.

Test Results

PreCoat Z31 Conversion coating for HDG has been thoroughly tested according to the highest test standards. PreCoat meets the following standards:

Paint adhesion

  • Cross hatch, according EN ISO 2409 / ASTM D3359
  • Boiling water test/wet adhesion
  • Impacttest, according EN ISO 6272-1 / ASTM D2794 / EN 13523-5.

Corrosion protection

  • Machu-test
    This is an accelerated corrosion test on test panels and construction parts according to Qualicoat specifications. The test is made in a warm environment. To create this environment the test panels are placed in the plastic container, which is placed in the Machu Test Bath. The test panels need to be scratched crosswise with a 1mm cutting tool before placing them in the warm moisture test chamber. The fluid content, temperature and remain time are specified.
  • Salt spray test
    Salt spray according to ISO9227/ Din50021/ ASTM B117.

Below image shows the test resultts after 500 hours of Neutral Salt Spray Test (NSS) in comparison to a chromium(VI) based pretreatment.

PreCoat Z31 chromefree pretreatment hdg

PreCoat Z31 versus Chromate conversion coating

Below table shows an overview comparison between PreCoat Z31 and a chromate conversion coating.

Chromate conversion coatingPreCoat Z31
Environmental impact-/-++
Corrosion protection and paint adhesion++++
Robust proces++++
Meets quality standardsQualisteelcoat, GSB, QualicoatQualisteelcoat, GSB, Qualicoat

Exceeding the market standard

HDG Pre-treatments have a huge range of requirements on a complex combination of zinc based alloys. This drives the need for close working relationships, consultation, testing and pilot line experimentation. With PreCoat Z31 AD Chemicals shows that replacing chromium-6 while maintaining the highest quality is possible.