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Thermally Sprayed Aluminium

Thermally Sprayed Aluminium

(OP)
We are being required by our customer to finish 316 stainless steel parts by thermally sprayed aluminium, with two epoxy coats on top of that in two different colours. I have found a vendor who will do it. I want to know how tough this finish is. I expect to be bolting the stainless steel parts together. The complete unit will be around 300kg, and we expect to be using an engine hoist to get it on and off carts and tables. Will the finish survive this?

--
JHG

RE: Thermally Sprayed Aluminium

The aluminum will require touch-ups due to handling damage [or the damage will be hidden by the epoxy paint]

RE: Thermally Sprayed Aluminium

(OP)
Duwed,

The whole point of the epoxy being two different colours is that we can see damage to the finish. Is it really that delicate?

This does not sound easy to touch up.

--
JHG

RE: Thermally Sprayed Aluminium

Will the Al sprayed metal actually bond to the stainless?

Never heard of that being tried before.

RE: Thermally Sprayed Aluminium

(OP)
racookpe1978,

We think our customer knows what they are doing and we have found a vendor that does it. The aluminium coating makes sense as a sacrificial coating, since aluminium and stainless steel are at opposite ends of the galvanic scale. This is all assuming we deliver the system with the coating intact.ponder

--
JHG

RE: Thermally Sprayed Aluminium

I doubt the painted surfaces will survive the high local contact stresses around the fastener holes or at the flange faces. It will also be difficult to spray the aluminum coating on the ID surfaces of the bolt holes.

RE: Thermally Sprayed Aluminium

The finish coat is never going to survive this for sure. Please note the below.

1. 1st coat : Sealer- to seal the pores
2. Top coat : for finishing purpose

Please keep in mind that even though the external coating to TSA is damaged, the pores will be still filled with the sealer (1st coat) if the damage is not so severe. So only a minor touch up on the top coat to be expected always.

In my opinion, I give importance to sealer more than top coat. By seeing this coating requirement on SS, I perceive that the customer concerned about corrosion protection (ESCC). Technically I think sealer will do it.

RE: Thermally Sprayed Aluminium

If the end use is in a reasonably high wet time environment the customer may want to worry about a little more than a bit of damage: see NACE Corrosion 2004, Paper 04203;

T A Sumon et al, Corrosion Engineering, Science & Technology, Vol 48, (7), 2013 pp 552 - 557

for example.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

RE: Thermally Sprayed Aluminium

For many years TSA and epoxy topcoats were used by the UK Highways Agency as the preferred means of protecting steel bridges which are often exposed to wet conditions and road de-icing salts. Handling and erection damage was never a particular issue for the specifications. However, long-term performance became something of an issue (see paper referred by Steve Jones) and many structures coated with TSA/Epoxy represent a legacy corrosion problem. In 2014 the UK HA updated the standard specifications and those no longer include TSA and epoxy over coats for protection of steel bridge structures.

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