Anticorrosive Performance of Zinc Phosphate Coatings on Mild Steel Developed Using Galvanic Coupling

M Arthanareeswari,M Tamilselvi,P Kamaraj

doi:10.1155/2013/673961

Abstract

The anticorrosive performance of zinc phosphate coatings developed by galvanic coupling technique on mild steel substrates using the cathode materials such as titanium (Ti), copper (Cu), brass (BR), nickel (Ni), and stainless steel (SS) is elucidated in this study. Thermal and chemical stability tests, immersion test in 3.5% NaCl, ARE salt droplet test, and salt spray test were carried out. The study reveals that the mild steel substrates phosphated under galvanically coupled condition showed better corrosion resistance than the one coated without coupling. The open circuit potential (OCP) of phosphated mild steel panels in 3.5% NaCl was found to be a function of phosphate coating weight and porosity of the coating.

Highlights

Phosphating is the most widely used metal pretreatment process for the surface treatment and nishing of ferrous and nonferrous metals
It was evident from the report that the extent of metal dissolution and coating formation is higher for mild steel substrates phosphated under galvanically coupled condition than the one coated without coupling [9]
3.1. ermal Stability. e percentage weight loss obtained for panels coated using galvanic coupling, subjected to 120∘C and 180∘C for 30 minutes, is given in Figures 1(a)–1(e) along with the uncoupled specimens for effective comparison. e percentage loss in weight was found to be more for substrates coated under uncoupled condition than those coated under coupled conditions

Summary

Introduction

Phosphating is the most widely used metal pretreatment process for the surface treatment and nishing of ferrous and nonferrous metals. Ough known to be in use since the 1940s [5, 6], the low temperature phosphating processes have become more signi cant today due to the escalating energy costs. E use of nitrites as the accelerator is the most common in low temperature-operated phosphating baths. A higher concentration of nitrite is required to increase the rate of deposition of phosphate coatings at low temperatures. E utility of the galvanic coupling for accelerating low temperature zinc phosphating processes was established recently [8,9,10,11,12]. E present work aims to study the thermal and chemical stabilities of panels phosphated under coupled and uncoupled conditions and their performance in 3.5% NaCl test, ARE salt droplet test, and salt spray test

Experimental Details

Results and Discussion

Conclusion