Corrosion of Alde Convectors

ScottG

@grassgd, this was my approach to getting (almost) all the glycol out prior to removal of the convector loop hoses.

DanWeitzel

I used the shop vac method before removing all the convectors.  This seemed to drain the system completely.  Refilled with the same original TF-1 (2016 T@B).  

grassgd

OK.  Drained and flushed entire system with tap water last night.  Today drained and disassembled everything.  

All aluminum parts (exchanger ends, check valve and short connectors) are all severely corroded.

All connectors and the check valve will have to be replaced.  The exchanger ends will have to be cut off enough to provide new ends with a few fins removed.  The aluminum pipe is just too thin to repair the pitting from the corrosion in my opinion.

I'll look at supply of straight pipe to replace the connectors which will allow me to lengthen them to account for the reduced exchanger length and let me cut the ends of the rubber hoses where there is concern due to excessive bulging.

That brings me to the question of what material.  Aluminum would be my last choice.  I know there has been some discussion on this forum about the material compatibility in the system.  I observed these materials in the Adle system:

Stainless at the boiler connections and the manual air bleed valve- no corrosion
Aluminum connectors, exchangers and check valve- highly corroded
Brass or bronze of the automatic bleeder -no corrosion

The only corrosion found appears to be on the aluminum parts in the confined areas under the rubber hoses. 

This leaves me to believe stainless steel or brass or bronze could be used to replace any of the aluminum parts without the risk of corrosion.  Copper pipe is a material radially available in 7/8 inch that could replace the connectors also but is not a material with proven performance in the system.   Any of the metal choices to replace the aluminum connectors could even be bent to replace the 90-degree rubber hoses and reduce the number of clamps/connections.  I am leaning toward stainless steel at first.

Any thoughts on the material to replace the aluminum connectors?

rh5555

Bear in mind that stainless steel has very poor thermal conduction properties compared to aluminum or copper.  I would stick with aluminum, but get the lengths hard anodized inside and out before assembly.  In my opinion, that is how they should have been manufactured in the first place.

grassgd

rh5555 said:

Bear in mind that stainless steel has very poor thermal conduction properties compared to aluminum or copper.  I would stick with aluminum, but get the lengths hard anodized inside and out before assembly.  In my opinion, that is how they should have been manufactured in the first place.

Thanks for your reply.  I understand that and I am only replacing the short connectors with stainless steel. That will not impact the thermal performance of the heat exchangers which are aluminum.

I agree hard anodizing is a good solution and I will contact a few companies near me to anodize the heat exchangers.  Concerned about the cost and minimum quantiles/cost for any anodizing.

DanWeitzel

grassgd said:

rh5555 said:

Bear in mind that stainless steel has very poor thermal conduction properties compared to aluminum or copper.  I would stick with aluminum, but get the lengths hard anodized inside and out before assembly.  In my opinion, that is how they should have been manufactured in the first place.

Thanks for your reply.  I understand that and I am only replacing the short connectors with stainless steel. That will not impact the thermal performance of the heat exchangers which are aluminum.

I agree hard anodizing is a good solution and I will contact a few companies near me to anodize the heat exchangers.  Concerned about the cost and minimum quantiles/cost for any anodizing.

Alde now sells the short connector made of plastic.  I used these to replace my corroded ones.

grassgd

DanWeitzel said:

grassgd said:

rh5555 said:

Bear in mind that stainless steel has very poor thermal conduction properties compared to aluminum or copper.  I would stick with aluminum, but get the lengths hard anodized inside and out before assembly.  In my opinion, that is how they should have been manufactured in the first place.

Thanks for your reply.  I understand that and I am only replacing the short connectors with stainless steel. That will not impact the thermal performance of the heat exchangers which are aluminum.

I agree hard anodizing is a good solution and I will contact a few companies near me to anodize the heat exchangers.  Concerned about the cost and minimum quantiles/cost for any anodizing.

Alde now sells the short connector made of plastic.  I used these to replace my corroded ones.

I would gladly use the plastic but if I cut the corroded convector heat exchanger ends off and trim the damaged ends on the rubber hoses, I may need to add a little extra length with homemade stainless steel connectors cut to the required length from bulk 7/8 inch stainless steel tube.  Are the plastic connectors expensive?

I also need a new check valve.  I should try to find out if Alde sells a plastic bodied one of those. 

DanWeitzel

grassgd said:

DanWeitzel said:

grassgd said:

rh5555 said:

Bear in mind that stainless steel has very poor thermal conduction properties compared to aluminum or copper.  I would stick with aluminum, but get the lengths hard anodized inside and out before assembly.  In my opinion, that is how they should have been manufactured in the first place.

Thanks for your reply.  I understand that and I am only replacing the short connectors with stainless steel. That will not impact the thermal performance of the heat exchangers which are aluminum.

I agree hard anodizing is a good solution and I will contact a few companies near me to anodize the heat exchangers.  Concerned about the cost and minimum quantiles/cost for any anodizing.

Alde now sells the short connector made of plastic.  I used these to replace my corroded ones.

I would gladly use the plastic but if I cut the corroded convector heat exchanger ends off and trim the damaged ends on the rubber hoses, I may need to add a little extra length with homemade stainless steel connectors cut to the required length from bulk 7/8 inch stainless steel tube.  Are the plastic connectors expensive?

I also need a new check valve.  I should try to find out if Alde sells a plastic bodied one of those. 

Here is a link to Alde products page with piping that may help you.  https://www.alde.us/our-products/?search=pip  Here is the plastic connector (stub) link.  https://www.alde.us/our-products/oe-7-8-16-mm/  You can find all Alde parts listed at their main web page.  https://www.alde.us/

ChrisK

Can you order Alde parts directly from them?

DanWeitzel

ChrisK said:

Can you order Alde parts directly from them?

Not sure, but you can call them & ask.

Fatman1966

Can all the ends easily be changed to the new plastic ones? If so how to they attach to the convectors? I’ve never had mine apart to see. Does the plastic connector just run the whole length of the convector and reconnect to the rubber hoses on both ends? 

DanWeitzel

Fatman1966 said:

Can all the ends easily be changed to the new plastic ones? If so how to they attach to the convectors? I’ve never had mine apart to see. Does the plastic connector just run the whole length of the convector and reconnect to the rubber hoses on both ends? 

Only the straight thru stubs (connectors) are plastic.  They just connect two sections of rubber hose together and have nothing to do with the convectors.

grassgd

Started working with the most corroded short convector heat exchangers.  Glass beaded the corroded ends.  The worst end needs to be cut off, shortening the overall length to provide a new surface. The other end looks ok.  



After cutting off the one end, the ends will be re-glass beaded then coated with 2 part epoxy primer.  I need to test my old epoxy primer before using on the convector ends.  If not still good will have to buy some.

Will keep posting progress but working slowly for a while.

fstop32

Lookin' good @grassgd!

ChanW

Thanks @grassgd! Following.... 

Chiprchuk

@grassgd
You are doing a great job. Would it be easier / cheaper to just replace them w/ new? I am thinking about your time & materials.

manyman297

I feel like what @grassgd is doing will provide much better protection than the same replacement part. The epoxy theoretically should provide some bulletproof corrosion protection.

grassgd

Chiprchuk said:

@grassgd
You are doing a great job. Would it be easier / cheaper to just replace them w/ new? I am thinking about your time & materials.

I am retires so time is not an issue.  Even if I bought new convectors, I would glass bead and 2 part epoxy coat the ends of any new convector to prevent corrosion for happening.  

grassgd

Some progress today.  Finished cutting off corroded ends on the convectors, glass beaded and applied two coats of 2 part epoxy primer.  

grassgd

I don't remember who came up with the idea of shortening the convectors to cut off the corroded ends, but sometime the simple solutions can be right in front of us and we can't even see it. 

Many thanks for whoever recognizer this solution which saves a lot of money instead of buying new convectors.

If I had to buy new convectors, I would consider replacing with fin tube base heater convectors with non-aluminum pipes- ie copper maybe.  Still not cheap but not aluminum.

Chiprchuk

@grassgd
I like the retired concept. Working hard to get there. As a side note - what is your setup for your bead blaster. 

grassgd

Chiprchuk said:

@grassgd
I like the retired concept. Working hard to get there. As a side note - what is your setup for your bead blaster. 

It is homemade from a two door warming rack.  The body is stainless steel. 

Sorry I don't know how to rotate the pics in the thread.  (Edited for photo rotation.  Moderator)

Built a plywood internal cone shaped insert in the bottom half with a plywood door/hatch.  Top door is plywood.  To fit the long convectors, I removed the grated working surface so I could stand them vertically and blast each end.

I works great.  Before getting this cabinet, I made a small one out of a dishwasher shell.  It worked good too and the door on the big unit is the door I used on the old dishwasher shell one.

pthomas745

I can rotate the pics for you..but I can't tell which way is up!

grassgd

pthomas745 said:

I can rotate the pics for you..but I can't tell which way is up!

The left side of the picture is the top - ie:the door with the gloves and window.  

Thanks!

DanWeitzel

Just musing but wondering if we could convert the Alde to a closed system using somthing like this automotive expansion tank.  This would introduce some pressure into the system as the glycol heated up, but guessing this wouldn't be to much (?).  Removing the O2 from the system might help overcome some of the corrosion issues (?).  

Horigan

For the convector end coating I would personally use marine heat shrink.  Make sure the convector ends are clean and smooth.  The adhesive in the marine heat shrink should do a good job of keeping the glycol from stagnating on the outer diameter of the convector end.

(MOD NOTE: This is a response to the following comment. Things got a little out of order during housekeeping!)

pthomas745

I've gone through this thread again and I can't say how impressed I am by the skills and abilities of this Forum group. 

I'm about to do a glycol exchange, and I will inspect my convector ends.  I have no visual evidence of much swelling...but, of course, the proof will come with the hoses off.

In this thread, there are several mentions of methods to protect the aluminum "stubs".  There are several suggestions: conformal coating, heat shrink, electrical or silicone repair tape, and one set of comments included "grease", but provided no examples.  Are any of these "better" to avoid the "attacks" by the trapped glycol?  Will improved "bolted" hose clamps prevent any glycol intrusion, so things like electrical tape or silicone tape should be reasonably secure?

Ease of install would be important to me, since I'm a novice at "heat shrinking" things.  Silcone tape ("repair tape" would be easiest.  Would the combo of tape and much improved hose clamps protect the stub ends?  Can the tape withstand a glycol "attack"?

And, Alde parts.  I've seen the comments about the difficulty of making Alde do the right thing and simply supply spare parts.  Seems that in Europe, or Great Britain at least, the concept of "right to repair" is respected.  I have found several vendors in the UK with quite an assortment of hoses, fittings, convectors.  It seems the magic number on many of the Alde's mentioned in this thread have 22mm type hoses/fittings.  The link below goes to one of several companies with long lists of Alde parts.  I emailed this company about whether they ship these to the US.

https://shop.caravanclub.co.uk/search/?term=alde

ScottG

I think @BrianZ was the first to document the use of heat shrink tubing to protect the convector stubs. However, IIRC, he did experience some degree of failure with that system after a time. Hopefully Brian will chime in here with clarification and details.

ScottG

MOD NOTE: Previous comments from @Horigan and ScottG have been moved here from Changing out the Alde fluid.

pthomas745

Thanks, ScottG, I know I duped posts.  I have the BrianZ heat shrink items in my Amazon wish list, and noted his issues with the "self adhesive" hose wraps.  (I will go back and look at them again).