Tin steel - how does it work?

The tinning of steel is used in many areas - such as in sheet metal processing, but also in the roof plumbing and occasionally in the body shop. What methods of tinning and how they work can be found in this post.

Purpose of tinning

When tinning, as the name suggests, a metal should be coated with a tin layer. Unalloyed steel and copper are most often tinned, but alloys are rarely used for tinning.

By tinning metals get the following properties:

  • Food compatibility
  • Solderability of metals
  • Corrosion protection, although this is usually not the intended main purpose of tinning (the corrosion protection by tinning is relatively good)

Methods for tinning

Basic methods for tinning are:

  • hot dipping
  • galvanic tinning
  • Reflow process

Each type of tinning has its own advantages and disadvantages, and produces slightly different differences. In practice, therefore, always the appropriate method must be selected.

hot dipping

In this way, metals were already tinned in ancient times. The workpiece to be tinned is simply immersed in a bath of liquid tin (melting point 231.9° C). The adhesion to the metal surface is very good in this approach, it also forms a stable alloy layer at the transition between metal and zinc, which further improves the adhesion of the coating.

Galvanic tinning

Tin coatings can also be applied by electroplating. The workpiece is placed in an electrolytic solution that also contains tin. If a voltage is applied, the zinc ions precipitate on the metal surface and adhere. The big advantage of this method is that you can do with very little tin, since the layers can be only a few microns thin. However, the liability is not quite as good, and especially with electronic components, occasionally problems can arise if the process is not carried out very carefully.

Reflow process

The so-called reflow process is a special form of galvanic tinning. After plating, the workpiece is again heated briefly to just above the melting point of tin in order to achieve a similarly good adhesion as in the hot dipping process.

Tips & Tricks

Copper can also be galvanized without electricity by simply immersing copper surfaces in a special tin salt solution. The method is particularly well suited for small workpieces (such as circuit boards), and very simple. It works only with copper, not with steel.

Video Board: Tinplate Girl #4 -- How to process tin cans for use in projects