No, you may not.
ECF Suppliers Terms of Service
11. Suppliers may not post in another Supplier's dedicated forum or in any Supplier's advertising thread without the express permission of the advertising thread/forum owner. This means an invite by PM or email by the owner of the thread, for that specific instance. If you have permission , only regular chat allowed - no business related posts allowed as it counts as advertising.
12. Suppliers may not post in another Supplier's thread without the express permission of the thread/forum owner. This means that if a Supplier starts an ordinary discussion thread, another Supplier should not post any adverts in that thread. An advert means any mention of your own products, or any link to your own site. Even if you have a sig link to your site, you should not post in another Supplier's thread as for this purpose (only) it counts as advertising. This is bad manners and may lead to acrimony.