The Development of Corrosion Resistant 2- and 1-K Waterbased Zinc-Rich Paints

From JPCL, August 2017

By Kenichi Nakamura, Roval, Japan; and Pascal Verbiest, Ph.D, EverZinc, Belgium

This article explains the formulation and performance of a waterbased (WB) zinc-rich paint, with 95-percent zinc content in the dry film, that is able to provide corrosion protection to steel equal to that of hot-dip galvanizing....

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Tagged categories: Coating Materials; Formulating; One-component coatings; Primers; Research and development; Two-component coatings; Waterborne coatings; Zinc

Comment from Mario Colica, (9/11/2017, 3:57 AM)

The comparation with hot dip galvanized surfaces 550gr/m2 is limited and partial. All technician know that the more the Zinc thichness the lomger is the resistence against rust. So if you employ thermal Zinc spray you can deposit up to 500 um 10 times more than HD galvanizing. No VOC problems with TSZn

Comment from Kenichi Nakamura, (9/13/2017, 9:41 PM)

Thank you for the comment. I can understand what you mean, but I think, thermal zinc spray requires very strict conditions such as ideal surface treatments. And it is not realistic to use it for large area or complicated area. On the other hand, cold galvanizing is easy to use in many practical situations.

Comment from Guy Decelles, (9/18/2017, 2:43 AM)

Intersting article, thank you. Have you considered the use of a Zinc flake pigment as oppossed to dust (spherical)? Best Regards

Comment from Kenichi Nakamura, (9/18/2017, 8:54 PM)

Yes, we use zinc flake in a solvent type paint. It has a lower electric resistance and a brighter color. However, it is generally covered with hydrophobic materials which are used in a manufacturing process. Therefore it is not compatible with a waterbased system. I wish it could be applied. Thank you for your comment.

Comment from HECTOR MEDINA, (9/19/2017, 8:54 AM)

In terms of surface prepartion Mr. Nakamura, what is the minimum requeriment for your product application? e.g SSPC-SP10, SP5 or a single SP3 or SP2?

Comment from Kenichi Nakamura, (9/19/2017, 8:21 PM)

In order to get the anti-corrosion performance that is equivalent to HDZ55, we recommend SP10 or SP5. However, this waterbased zinc rich paint could be compatible with SP3 or SP2.

Comment from David Grove, (9/20/2017, 7:28 AM)

In Fig.1, what is the darker layer at the interface to the substrate? Is it similar to the Gamma layer or Delta layer in HDG? Excellent article!

Comment from Kenichi Nakamura, (9/20/2017, 9:07 PM)

I can not explain that correctly, but I found some chemical interaction there by analyses. I would like to figure out that in a next article. Thank you for the motivating comment.

Comment from Christian Favennec, (9/21/2017, 12:35 AM)

Good article and interesting approach. Which kind of CCT do you use, and what salt concentration? Did you perform any comparative adhesion test between HDG and coating, and any electrochemical test to evaluate electrochemical potential evolution? Did you evaluate the Influence of roughness and cleanliness on the coating performance? it could also be interesting to evaluate the performance in comparaison with solvent base rich paints.

Comment from Kenichi Nakamura, (9/22/2017, 2:09 AM)

The condition of CCT is below. 1. Salt spaying 30±2?, 0.5h 2. Moistening 30±2?, 95±3%RH, 1.5h 3. Hot air drying 50±2?, 2h 4. Warm air drying 30±2?, 2h (1?2?3?4?1..) Salt concentration is 5wt%. Adhesion strength of the coating is much weeker than HDZ, but it is about 10MPa. The electrochemical potential of the coating is almost the same as that of HDZ: -950mV. The anti-corrosion performance of the coating is influenced by roughness or cleanliness. Ideally speaking, more than 25µm of roghness and SP10 of cleanliness are recommended. Both waterbased and solvent type have almost the same anti-corrosion performance. Thank you for the pointed question.

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