Patent ID: 9592533
Date: 2017-03-14
CPC Classifications: B05D,B32B,C21D,C23C,C25D,Y10T

Claim:
1. A process for tin coating a metallic substrate having a top surface, comprising the following steps: providing a two-layer coating on the top surface of the metallic substrate, wherein the two-layer coating comprises a tin layer formed on the top surface of the metallic substrate and a metal layer formed on the tin layer, wherein the tin layer has a bottom surface that defines a bottom surface of the two-layer coating, wherein the metal layer has a top surface that defines a top surface of the two-layer coating, wherein the metal layer is made of a metal material different from tin; and carrying out a diffusion annealing operation on the two-layer coating to allow heterogeneous diffusion of the metal material into the tin layer in a direction from the top surface of the two-layer coating to the bottom surface of the two-layer coating, thereby creating a modified alloy layer having a top surface that is the same as the top surface of the two-layer coating and a bottom surface that is the same as the bottom surface of the two-layer coating; wherein the concentration of the metal material decreases from the top surface of the modified alloy layer to the bottom surface of the modified alloy layer; wherein the modified alloy layer has a thickness defined between the top surface of the modified alloy layer and the bottom surface of the modified alloy layer; and wherein the metal material is present partially in the modified alloy layer, starting from the top surface of the modified alloy and extending only to 30%-50% of the thickness of the modified alloy layer; wherein the metallic substrate is a profiled or a round wire; and wherein an intermediate layer made of nickel is applied to the metallic substrate before the tin layer is applied, and wherein the diffusion annealing operation encompasses at least the tin layer and the metal layer.