Halcyon Aluminium Backplate with stainless steel bolts for Backpad?

[Heat Miser]

I know that I sound like I am very unobservant;

but a couple of years ago I bought what I thought was supposed to be a 30lb Halcyon Infinity BCD with steel backplate and the full backpad covering the backplate and it had the single tank adapter.

Yesterday whilst putting together a set of doubles, I was pulling the backpad off, and it was a real stuggle. Turns out I have an Aluminium backplate. And they have attached the the backpad using stainless steel bolts and washers. There is corrosion right around the plate from galvanic reaction.

Is this common, or have I been sold a mishmash the shop put together?

Good news I use 4lb less weight than I ever thought I did, It allways surprised me the amount of weight I had compared to everyone else.

Another question ... if I take the old backpad and attach it to a carbon fibre backplate using the old bolts am I encourgaing more galvanic reaction.

 

[Alaskan Scuba Dude]

If stainless steel isn't in direct contact with aluminum there shouldn't be a problem.

 

[Heat Miser]

That my point It has stainless steel bolt directly attached to the aluminium. Photos attached. I’m concerned I am just going to have the same problem on my carbon fibre backplate. Do Halcyon really ship it like this? Or should there be some plastic washers etc. in between the backplate and the bolts that stap the back pad on?

 

[Russjstewart]

I suspect your s/s nuts and bolts will corrode before your carbon fibre backplate

Galvanic Corrosion of Metals Connected to Carbon Fiber Reinforced Polymers

The use of carbon fiber-reinforced composites is growing thanks to their high strength and light weight. This material poses new challenges in terms of mitigat

www.corrosionpedia.com

Stainless Steel​

There is no evidence of the formation of corrosion for stainless steels coupled to carbon composite. However, it is reported that some types of stainless steels (such as types 410 or 301) are susceptible to localized corrosion (pitting corrosion and crevice corrosion) when they are connected to a carbon composite in aerated 3.5% NaCl (simulated seawater). It is believed that the pitting corrosion will be enhanced by increasing Ac/Aa. (For more information about pitting corrosion, see A Look at High Nitrogen Stainless Steels .)

 

[rongoodman]

Toss the backpad?

 

[formernuke]

If stainless steel isn't in direct contact with aluminum there shouldn't be a problem.

Go back to metallurgy school. Dissimilar metals touching increases the risk for galvanic corrosion.

 

[Heat Miser]

Toss the backpad?

Yes that was my initial reaction.

The next one was how can something you pay a premium for, can be put together so shoddily.

 

[rongoodman]

Other than not selling the pad in combination with an aluminum plate, it isn't clear what you think Halcyon should have done. How long had you left the pad attached to the plate prior to noticing the damage?

 

[Heat Miser]

Other than not selling the pad in combination with an aluminum plate, it isn't clear what you think Halcyon should have done. How long had you left the pad attached to the plate prior to noticing the damage?

Plastic washers between the bolts and the aluminium for a start. Plastic coated bolt and nuts. Aluminium eyelets for the back pad to match the backplate.

The back pad is not designed to be removed after every dive, it fully covers the front of the backplate and back of the plate showed no sign of corrosion, because it was under the stainless steel bolt heads. The back plate was directly attached to a stainless steel single tank mount using stainless steel bolts which also corroded the Ali plate (yet again behind the fully covering back pad)

I would expect someone at Halcyon would have worked out, this was going to be a problem. I understand it when I’m fastening on my cylinder clamps to stages.

That is why I ask, did someone at the shop make up a mish-mash set and sell it to me? Or is this a common way to ship from the factory?

 

[agmason]

You can get plastic washers and a sleeve if you still want to use stainless steel bolts and nuts with the aluminum backplate. You should have no issues with carbon fiber as it's a non-ferrous stable compound and will not react with Stainless Steel.