Repairing wet or submerged materials presents a particular challenge: choosing an adhesive that can cope with moisture during application, rather than simply resist water once cured. An underwater epoxy adhesive such as Alpha SAS328 is designed for these demanding conditions.
Supplied in a compact 25ml twin syringe, SAS328 is a two-part, toughened epoxy for bonding materials including concrete, steel, stone, brick and wood. This guide explains where it may be useful, how to prepare a repair and what to check before starting.
What makes underwater bonding different?
A waterproof adhesive and an underwater epoxy adhesive are not automatically interchangeable. Some products resist water after curing but require completely dry surfaces when applied. Using them on wet materials can result in poor adhesion, even when the finished adhesive itself is water-resistant.
Alpha SAS328 is specifically developed for wet, damp and submerged applications. However, moisture tolerance does not remove the need for preparation. The adhesive still needs contact with a sound surface, rather than dirt, loose rust, algae or failing coatings.
Before selecting a product, establish whether the area is damp, occasionally splashed or continuously submerged.
What is Alpha SAS328?
Alpha SAS328 is a room-temperature-curing epoxy combining a resin and hardener in a 1:1 mixing ratio. When thoroughly mixed, the components form a beige, slump-resistant paste.
Its paste consistency helps keep the adhesive in the joint, while its gap-filling capability accommodates spaces up to 5mm. This can be useful where mating surfaces are uneven or do not fit closely together.
As an underwater epoxy adhesive, SAS328 offers a combination of water resistance, mechanical strength and impact resistance. Its 25ml pack is worth considering for localised repairs and smaller assemblies, with the quantity required depending on bond area and adhesive thickness.
Which materials can it bond?
SAS328 is designed for a range of construction and engineering materials. Suitable substrates listed by Alpha include:
- Concrete, stone masonry and brick.
- Wood and steel.
- Fibreglass and ceramic tiles.
- Certain plastics, including ABS and rigid PVC.
This makes it a potential option for repairs involving different materials, such as steel bonded to concrete.
However, identifying the exact substrate remains essential. Rigid PVC and flexible PVC behave differently, while a painted metal component presents a coating rather than bare metal at the bonding surface. Test unfamiliar materials and confirm suitability before committing to the repair.
When should you consider an underwater epoxy adhesive?
SAS328 may be relevant where drying the bonding area is difficult or where materials must be joined in a wet environment. Alpha lists applications across marine maintenance, structural bonding, underground conduits and general repairs.
The important question is what the joint must do. Bonding two rigid components together is different from sealing a moving joint or stopping a pressurised leak. Do not assume that suitability for underwater bonding makes a product appropriate for every water-related repair.
Consider the joint’s movement, loading, accessibility and exposure conditions before choosing the adhesive.
How to prepare and apply Alpha SAS328
Successful use of an underwater epoxy adhesive begins before mixing. Check that the components fit, plan how to hold them in position and prepare everything needed for application.
1. Prepare sound bonding surfaces
Remove contamination, loose coatings, rust and marine growth. Follow Alpha’s preparation instructions for the substrate. For concrete, the manufacturer specifies at least 28 days’ curing and a minimum compressive strength of 25MPa.
2. Mix the components thoroughly
Dispense equal parts of resin and hardener. Mix until the colour is consistently beige, with no unmixed streaks. Simply dispensing both components together does not complete the mixing process.
3. Apply and position
Apply the mixed adhesive to one prepared surface, bring the components together and secure them in their final position. Plan supports beforehand so the assembly does not move while strength develops.
4. Allow sufficient curing time
At 20°C, the stated working time is approximately 45–60 minutes. Handling strength develops in around six hours, with full cure around 24 hours. These are typical figures; actual conditions can affect performance.
Important limitations before starting
An underwater epoxy adhesive should be selected against the complete repair requirements. For SAS328, Alpha specifies underwater application temperatures between 4°C and 35°C and states that underwater placement should only be undertaken by certified, experienced diving contractors.
Do not assume approval for drinking-water systems, aquariums or food contact. These applications require specific confirmation. Read the safety data sheet and follow its handling and protective-equipment requirements.
For the manufacturer’s application instructions and technical figures, consult the Alpha SAS328 technical datasheet.
Where to buy Alpha SAS328 25ml
If you need an underwater epoxy adhesive for a suitable wet-surface bonding application, buy Alpha SAS328 25ml here.
Unsure whether it suits your repair? Contact us with the materials, approximate bond area and water conditions so we can help assess the application before you order.