Product Introduction

Heat-resistant topcoat
5K189
Nippon Hyomen Kagaku Kabushiki Kaisha R & D center

Introduction

Treatment process

In Japan, most zinc plating and zinc alloy plating are

5K189 can be treated using the same process as

generally treated with a conversion coat after plating.

conventional organic-mineral topcoats.

However, there are specifications in which a topcoat

Zinc-based plating → Chemical passivation →treatment is further applied after the conversion coat
treatment to improve corrosion resistance and adjust/(Post dip) → Drying → 5K189 → Stand →improve fastening characteristics.
Although there are various types of topcoats, aqueousCentrifugal drying → Drying

organic-mineral topcoats are currently the most widely used

* Of the above treatment processes, water rinsing isfor zinc plating and zinc alloy plating because they can be

performed after zinc-based plating and chemical passivation.

selected according to the required friction coefficient, areeasy to handle, and do not require exhaust facilities. 1

Mechanisms

However, organic-mineral topcoats have low heat

Aqueous organic-mineral topcoats consist of a base resin

resistance of the film, and if they are exposed to high(water-soluble resin, resin emulsion, resin dispersion, etc.)

temperatures after treatment, discoloration will be cased andcombined with an inorganic binder and wax for friction

corrosion resistance decreases.

modifier as necessary. Base resins and wax used in general

Nippon Hyomen Kagaku has developed a new aqueousorganic-mineral

topcoats

have

many

heat-sensitive

organic-mineral topcoat 5K189 that provides excellent

components, causing thermal degradation of the topcoat film.

corrosion resistance even after heating. We will now

5K189 uses a newly developed base resin with high heat

introduce the technology behind this agent.

resistance, and by reviewing the component ratio with the
inorganic binder, excellent heat resistance was achieved.

Product SummaryFigure 1 shows a structure model of general organic-mineral

5K189 is aqueous topcoat for zinc plating and zinc alloy

topcoat and 5K189 film.

plating. 5K189 is treated on trivalent chromium conversion
coatings to win excellent corrosion resistance and maintain

Base resin

performance after heating.
Features・

conversion coatings.
High corrosion resistance can be maintained even after
heating (up to 200°C) with little change in appearance.
・Base resin

Wax
Topcoat layer

Topcoat layer

Trivalent chromium
passivation coating layer

Trivalent chromium
passivation coating layer

Zinc-based
plating

Zinc-based
plating＜General organic-mineral topcoat＞＜Heat resistant topcoat 5K189＞

Excellent corrosion resistance and glossy appearance
can be obtained by treating over trivalent chromium

・

Inorganic binder

Since it is dip treatment, it can be treated with the samelevel of facilities as post-treatment of plating (no needfor exhaust or explosion-proof facilities).

Figure 1: Film Structure of Aqueous Organic-mineralTopcoat
Revised 20230714 JASCO Nippon Hyomen Kagaku Kabushiki Kaisha 1

[Product Introduction] Heat-resistant topcoat 5K189

After heating at 200°C for 24 hSalt spray test0h

120 h

240 h0h120 h240 hWithout topcoat

Heat-resistant
topcoat
5K189
Conventional
topcoat(organicmineral)(surface treatment: zinc plating + trivalent chromium passivation coatings)

Figure 2: Salt Spray Test (JIS Z 2371) Results of 5K189 Treated Products
Figure 2 shows the salt spray test results of 5K189
treated products. Treatment with 5K189 and conventional

In closingorganic-mineral topcoat improves corrosion resistance in

5K189 is aqueous organic-mineral topcoat that is easysalt spray tests. However, the conventional organic-to handle and can dramatically improve the corrosion andmineral topcoat discolors when heated at 200°C, resulting

heat resistance of galvanized products simply by dippingin a significant decrease in corrosion resistance. On thetreatment. Although sufficient verification is needed, newother hand, 5K189 shows almost no change in appearance

solutions may be created, such as application to heat-and maintains its corrosion resistance even after heating

resistant parts that have been difficult to handle with zincat 200°C.

plating. We will continue to closely monitor trends inFigure 3 shows the measured coefficient of friction of

topcoat technology and the market, and as a chemical

5K189 treated products. The total coefficient of friction

manufacturer, we intend to conduct further research toof 5K189 is 0.3 to 0.4. 5K189 tends to have a higher

propose new technologies and products.

coefficient of friction than conventional organic-mineral
topcoats because it does not contain friction modifiers

Literaturesuch as wax. 5K189 friction modification is a future task.

1: Hideo Susa; J. Surf. Finish. Soc. Jpn. Vol.70, No. 8, pp.
388-393 (2019)

0.600
Total coefficient of friction

Average+3σ-3σ

0.500
0.400
0.300
0.200
0.100
0.000

Without topcoat
5K189(surface treatment: zinc plating + trivalent chromium
passivation coatings)

Conventional topcoat(organic-mineral)

Figure 3: Coefficient of Friction (JIS B 1084) of 5K189
Treated Products
Revised 20230714 JASCO Nippon Hyomen Kagaku Kabushiki Kaisha 2