Effects of Phosphorus-Free Conversion Process Parameters on the Adhesion Properties of Electrophoretic Paint Film

ZHANG Cheng

doi:10.16577/j.issn.1001-1560.2025.0035

Materials Protection >

2025 , Vol. 58 >Issue 2: 156 - 161

DOI: https://doi.org/10.16577/j.issn.1001-1560.2025.0035

Effects of Phosphorus-Free Conversion Process Parameters on the Adhesion Properties of Electrophoretic Paint Film

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(Beijing Hyundai Motor Co.， Ltd.， Beijing 101300， China)

ZHANG Cheng(1986-)， Junior Engineer， Research Focus: Antomobile Coating， Tel.: 13426178483，E-mail:zhangc4＠bhmc.com.cn

Received date: 2024-06-11

Revised date: 2024-10-08

Accepted date: 2024-10-10

Online published: 2025-03-21

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Abstract

To address the issue of insufficient adhesion strength of electrophoretic paint film on the cold-rolled steel plates beneath the doors of white body vehicles， this study compared the effects of various process parameters， including phosphorus-free conversion treatment time， electrophoretic baking temperature， free fluoride ion concentration， and ferrous ion accumulation， on the adhesion of electrophoretic paint film.Through random on-site inspections of thickness and adhesion strength of the electrophoretic paint film， it was found that when the coating thickness of the phosphorus-free conversion layer exceeded 40 mg/m2， adhesion failure of the electrophoretic paint film on the cold-rolled steel beneath the doors of white body vehicles was likely to occur.Based on both on-site data and laboratory simulation tests， the following conclusions were drawn: only by strictly monitoring the non-phosphorus conversion bath in accordance with the on-site process parameters， controlling the ferrous ion content below 25 mg/L and the fluoride ion concentration at 20～40 mg/L，can the adhesion of the electrophoretic paint film on the plate at this position reach the standard and adapt to the mass production process on site.

Key words： phosphate-free conversion; process parameters; electrophoretic paint film; adhesion; field application

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ZHANG Cheng . Effects of Phosphorus-Free Conversion Process Parameters on the Adhesion Properties of Electrophoretic Paint Film[J]. Materials Protection, 2025 , 58(2) : 156 -161 . DOI: 10.16577/j.issn.1001-1560.2025.0035

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