Metal finishing Q&As since 1989

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Weldment/assembly seeping cutting fluid... Ruining paint

2002

Hello,

As some of you know, I am a chemical engineer working for a engineering/manufacturing facility that build transport equipment for primarily the US military. We fabricate, machine weld and assemble both ferrous and non-ferrous parts. Of course someone has to keep all of this metal from deteriorating, and that is where I come in. We do 99% of our organic finishing in house. Primarily we use an organic wash primer for pretreatment and apply various liquid spray primers and topcoats. Anything requiring plating, conversion coating, we outsource. Now my question does not really have to do with the finishing, per se, but with a phenomena that is ruining my finishing...

We take two 50 foot long, 6 X 12 inch C-shape Steel channels, and weld them together making a hollow channel. The weldment gets reinforcing plates welded in numerous areas. We have very large 'saddle' castings which are C-shaped that are placed 'around' three channels. The saddle casting, reinforcing plates and channels are all drilled (with cutting fluid) and riveted together. A polysulfide sealant is placed between faying surfaces and eventually the entire assembly gets painted. We are currently having a problem with cutting fluid seeping out from these faying surfaces. Bubbling both the sealant and the paint. Also cutting fluid gets on, into, the paint before it cure, seeps under the paint from the back... all sorts of problems.

I was wondering if anyone else has ever encountered something similar. And what if anything they would suggest as a possible fix. We have tried to drain the tubes, but do not get every thing out, we have added more sealant, heated the local area prior to sealing the channel completely...

I know this doesn't really fit any category, and is a little off subject, but thought I may luck out and find someone who has been here.

Thanks for you time!

Kelly L. Jones
- West Plains, Missouri

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2002

Kelly, some questions:

- The cutting fluid, is it oil- or waterbased?
- What do you do with the parts between riveting and sealing and between sealing and painting (cleaning, washing)?
- Curing time/temp of the paint
- Type of paint used?

Remmelt Bosklopper
- Enschede, The Netherlands

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And I thought I had been pretty thorough, but I missed some pretty simply facts.

1. It is a water based fluid.
2. After riveting the area is cleaned with alcohol and dried. Then sealed. Then painted within 2-24 hours.
3. The paint can ambiently cure, but we accelerate it at a temperature of 150 °F for approx. 2 hours.
4. It is a 2-component epoxy primer followed by a two component polyurethane topcoat. Both p[rimer and topcoat are exposed to the 150 for two hours. So there are two cure cycles.

Respectfully,

Kelly Jones
- West Plains, Missouri, USA
2002