Letter 13456

Plating on titanium 

Need to electrolytic nickel and silver plate small titanium tubes ( 3x 1 cm). Contact point only through small hole in base ( two pin standard jig ). Difficulty in activating surface before nickel strike especially after stripping rejects in nitric acid.

Brian Grieves
- Wakefield, West Yorkshire, UK

Titanium is a very difficult metal to activate and to keep it activated as it processes from one tank to another. You fail to say what your activation step is. There are several published processes and most are many stepped.A lot will depend on how good you need to have the adhesion, good enough to get by or great.

James Watts
- FL

I have never done this, but I was once told by a very reputable electroplater titanium can be electroplated. The important things is to get good adhesion, this is accomplished by using a compressive deposit and mechanical abrasion. Mechanical abrasion can be achieved with grit blasting, vapour blasting, glass bead blasting. Use a nickel strike solution to assist adhesion.

Titanium can also be electrochemically processed by etching in a solution of:
NH4HF 10-40g/l
H2SO4 5%v/v
Temp 20C
Leave for 30 secs or more AFTER gassing starts.

The titanium is then activated in:
HF(40%) 50-70ml/l
HNO3 50-100ml/l
H2O2 100-200ml/l
Temp: RT
Time 5-10 secs

Once activated, the titanium can be strike plated with Woods Nickel. It is essential that NO RINSING takes place between the activation and strike plating. I believe this was documented in Trans. IMF. 1966 p74

There are a couple of of other activation solution compositions for pure or alloyed titanium:

a) Pure Ti
HCL (35%) 500ml/l
TiCl4 (15%) 10-20ml/l
Additive 1g/l sulphuric and sulphamidic acid
Temp: RT
Time: Until uniform gassing

b) Ti Alloys
DMF 400-600ml/l
HF (40%) 100-150ml/l
Additive 2 2-3g/l aryl compounds
Temp: RT

For a nickel strike, use a Woods nickel or one of the following:

a) Woods nickel strike:
NiCl2 240g/l
Conc HCl 12ml/l
Temp 35-50C
c.d. 5-10A/dm2
Time 1-3 minutes

b) Nickel sulphamate based:
Ni(NH2SO3)2 320g/l
H3BO3 30g/l
HCl 1.2% vol
pH 1.5 max adjust with NH2SO3H
Temp: 27-38C
c.d. 1-10A/dm2
Time 30-60 secs.

Alternatively, a fluoride based nickel strike:

c) NiSO4 200g/l
H3BO3 20-30g/l
NH4HF 10g/l
pH 1.5-2.0
Temp: 27-38C
c.d. 5-10A/dm2
Time: 1-3 mins.

Once metallised, heat treat to 190-400C as this improves adhesion.

I hope this solves your problem.

Trevor Crichton R&D practical scientist - UK

Titanium absolutely can be plated with very good adhesion, but it is a process that demands attention. A company that I worked for was one of the first in the US to do it. I have seen about 20 different processes, all claiming to be the best. All were multi step prep. Whoever is going to do it should do a thorough research of the literature lab trials and then pilot plant the two that look the best. It is not like plating steel.

James Watts
- FL

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