The purpose of this work is to study the behavior of electroless Ni coatings on SAE 1020 steel in aqueous 4% NaCl solution. An aqueous solution with NiSO4.6H2O (Nickel Sulfete), NaH2PO2.2H2O (Sodium Hypophosphite), C3H6Q3 (Lactic Acid), C3H6O2 (Propionic Acid) and Pb(NO3)2 (Lead Nitrate) as the basic ingredients of the bath was selected for the autocatalytic deposition of Ni, with an average deposit rate of c.a. 19 μm/h.

Steel coupons were immersed in the bath for 1, 2, 3 h in the original solution, renewing with fresh solution every hour. Once coated with nickel, the coupons were subjected to heat treatment for 1, 2, and 3 h at 400 °C, measuring hardness to determine how it is affected by thermal treatment. Salt-spray tests were carried out at 30 °C in line with ASTM B117-75 and DIN 50907 standards. The corrosion rate was determined by potentiodynamic polarizing curves (0.28.10-3 Vs-1), using a 4.0% w/w NaCl solution. Corrosion resistance was higher in the coupons that underwent 2-3 h of heat treatment and 2-3 h plating time. Corrosion rate varied between 2.41 and 3.40 μm/y. The surface of the coupons in the salt spray chamber had a good appearance at the end of the 568-hour test.

Subject
Nickel coatings, Coatings, Composition, Corrosion rate, Metal surfaces, Phosphorus, Steel, Corrosion resistance, Corrosion coupons, Deposit corrosion, Nickel, Hardness, Heat treatment
Keywords:
Electroless nickel, mild steel, corrosion, heat treatment, hardness
© 1997 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1997
Association for Materials Protection and Performance (AMPP)
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