If the trailers are imported from China, yep I'd be concerned with steel quality. Regalving can be done but it's not cheap as they have to remove the existing galv. At a guess you'd be looking at around $2kg maybe more. Questions to as them is will it need a double dip, and cost of galv removal. Ferogalv now have massive baths so need for double dipping.

Wow! $3500 is cheap! I'd be sus on any steel coming from China at that price though....

I got Hartways in canningvale to do my similar size trailer, the entire project cost me about $950 and the trailer is as good as new. This included buying new ubolts for the springs and some new nuts and washers. They will quote you $2.50 per KG or $125 ex GST per meter. I ended up wheeling and dealing and got my price down going for the per KG rate.

Just a note here: Most threads on mine were BSW and I think its because they are cheap to buy. Problem is they aren't as common and I had trouble getting nylocs in gal for BSW, so you need to use loctite or buff and reuse and then hammer with gold gal. I also changed all the roller bolts to Stainless UNC and use antiseize on everything and then hammered it all with fish oil.

You need to dissasemble into individual parts. Make sure you measure and note everything if you want the trailer balance and boat position to easily go back the same.

I didn't do springs, axles or hubs. but everything else got done and it was a strip and dip. You could do axles if you want to mask the machines surfaces. Mine were originally galvanised are weren't that bad so I just sprayed them up with silver gal for mostly cosmetic reasons. Springs the same but I didn't want to play around with taking the packs apart and risk heat affecting the springs, so I left these.

If doing any welding, look closely at flux inclusions because the galvinising definately show this up. Best to use mig or tig with gas if you have access... even then, brush the welds really well.

You will need to get any items with thick flakey rust sand blasted first as the acid dip won't remove this.

I'm stoked with the result and this trailer is now like new! I changed to conical rollers and converted some of the removed wobble rollers to side guide rollers and now the boat easely drives straight up and self centres to the exact centre... (well that was on the one and only use after the job. hopefully it wasn't a fluke)

Hopefully corrosion under control for 10 years now...

PM me if you want to know more or have a look at mine..

 Did mine a couple of years ago , cost around $650 and that was including freight kwinana bunbury and return.Take photos then do it yourself replace any sus bits most trailer parts r cheap.Good luck.

p.s my trailer is a dual axle McKay. 

 $3:30/kg to remove old galv and re:galv. last time I did my boat trailer at Hartways, $2:20/kg clean

Gunner 

 cheers for the input fellas ! Looked at one today that was a re gal and the base frame of the trailer measured at 2 mm walls so I think I will pass on that and keep looking. Maybe an Ali one out there. Keep up the good work!

Leon