NIPPON STEEL CORPORATION

Post-paintability

ZP treatment
Chromium-free phosphate treatment

① Superior paintability

This material has superior paint adhesion, making it possible to omit the process of pre-paint surface preparation.

② Excellent corrosion resistance after painting

Processed and spot welded parts of the material also exhibit excellent corrosion resistance after painting.

③ Superior compatibility with the environment

The resultant material is friendly to the environment because its film is entirely free of chromium

④ “Plus “ high coating performance

ZP-Five different types of chromium-free treatments

Quality characteristics

Sample Elution of chromium Corrosion resistance
(before painting)
(8 hrs of SST)		 Paint adhesion Corrosion resistance after painting
(150 cycles of CCT)
Name Treatment Primary adhesion Secondary adhesion
ZAM® ZP treatment No elution OK OK OK good
Galvanized Steel Chromate treatment Elution OK OK OK OK
Electrolytic Zinc-coated steel Chromate-free Phospahte treatment No elution OK OK OK normal
The above data is an example of our products.
Elution of chromium : Amount of chromium elution measured after the specimen has been immersed for 3 minutes in boiling water
Corrosion resistance : Salt spray test (JIS Z2371) 8 hrs ( ○ : White rust occurrence 10% or less, × : white rust occurrence more than 10%)
Paint adhesion : Primary adhesion : Lattice pattern (1 mm) cutting and cellophane tape peeling test ( ○ : no peeling, × : peeling)
Paint adhesion : Secondary adhesion : After immersion for 2 hours in hot water (90°C), lattice pattern cutting and cellophane tape peeling test ( ○ : no peeling, × : peeling)
Corrosion resistance after painting : Combined-cycle test (JIS G0594) 150 cycles (superior ◎ ○ △ inferior)

Paint adhesion for ZP treatment

ZAM®ZP treatment
Secondary adhesion : ZAM® ZP treatment
Galvanealed steel Chromate treatment
Secondary adhesion : Galvanealed steel Chromate treatment
Electrolytic Zinc-coated steel Chromate-free Phosphate treatment
Secondary adhesion : Electrolytic Zinc-coated steel Chromate-free Phosphate treatment

Secondary adhesion

Painting conditions

Acrylic paint (30μm: spraying + baking finish)

Samples

ZAM® - ZP treatment : Thickness: 0.8 mm, one-side coating weight : 47 g/m2
Galvanealed steel Chromate treatment : Thickness : 0.8 mm, one-side coating weight : 40 g/m2
Electrolytic Zinc-coated steel Chromate-free Phosphate treatment : Thickness: 0.8 mm, one-side coating weight : 10 g/m2

Paintability evaluation

Secondary adhesion : After immersion for 2 hours in hot water (90°C), lattice pattern cutting and cellophane tape peeling test

Corrosion resistance after painting(after 150 cycles of CCT)

Corrosion resistance evaluation

Combined-cycle test (JIS G0594)
1 hr of SST → 4 hrs of drying (50°C) → 3 hrs of BBT (50°C, 95%RH or higher)
ZAM® ZP treatment
Cross-cut section : ZAM® ZP treatment
Galvanealed steel Chromate treatment
Cross-cut section : Galvanealed steel Chromate treatment
Electrolytic Zinc-coated steel Chromate-free Phosphate treatment
Cross-cut section : Electrolytic Zinc-coated steel Chromate-free Phosphate treatment

Cross-cut section

Spot welded section : ZAM® ZP treatment
Spot welded section : Galvanealed steel Chromate treatment
Spot welded section : Electrolytic Zinc-coated steel Chromate-free Phosphate treatment

Spot welded section