Prepare the Surface Before You Trust the Bond

Soudal primers help trades prepare concrete, masonry, plasterboard, powder-coated aluminium, plastics & other compatible substrates before selected sealants, adhesives & waterproofing systems are applied. The important part isn't simply deciding to use a primer—it's matching the preparation product to the substrate, surface condition & product being installed over it.

Porous concrete doesn't behave like powder-coated aluminium. A dusty mineral substrate creates different adhesion problems from PVC, glass or a coated metal profile. Even two porous surfaces can require different preparation depending on whether the next layer is polyurethane sealant, silicone, hybrid polymer or waterproofing membrane.

That distinction matters because primer can't compensate for loose material, contamination, the wrong substrate preparation or an incompatible product combination.

For sealing & bonding work that follows preparation, browse Adhesives & Tapes. For porous substrates being prepared as part of a wet-area system, explore Waterproofing & Damp Proofing.

What Are Soudal Primers?

Soudal primers & activators are surface-preparation products used before compatible adhesives, sealants or waterproofing products.

The range includes distinctly different preparation products:

► Primer 100 – a polyurethane-based primer for porous surfaces, particularly where polyurethane sealants are being used
► Primer 150 – a porous-surface primer suited to compatible silicone, hybrid & SMX polymer sealants
► Soudaprim DP – a solvent-free deep primer for porous or absorbent mineral substrates before compatible waterproofing membranes
► Surface Activator – a combined degreaser & adhesion promoter for suitable non-porous surfaces including metals, glass & selected plastics
► Activator Spray 601 – a quick-drying adhesion promoter particularly suited to powder-coated aluminium & selected difficult non-porous substrates

The first decision is usually porous or non-porous. The next is what product will be applied after preparation.

Why Choose Soudal Primers?

Here's a useful way to think about surface preparation.

Put a drop of water onto unfinished concrete & another onto powder-coated aluminium.

The concrete may absorb it. The aluminium won't.

Those surfaces clearly aren't asking for the same preparation.

On porous substrates, the job can involve controlling absorption, improving adhesion or consolidating a suitable absorbent surface.

On dense, non-porous surfaces, preparation may instead involve cleaning, degreasing & promoting adhesion at the interface.

Then there's another variable: what are you putting over it?

A substrate being prepared for polyurethane sealant doesn't necessarily require the same treatment as one being prepared for silicone, hybrid polymer or a liquid waterproofing membrane.

That's why “prime it first” isn't specific enough. Good preparation means matching surface behaviour + surface condition + following product + exposure conditions.

Common Applications

Expansion Joints in Concrete & Masonry

Movement joints place repeated stress on the sealant-to-substrate interface.

On suitable porous joint faces, the correct primer can help prepare the surface before a compatible sealant is installed. Selection should consider both the substrate & sealant chemistry rather than choosing a primer simply because the joint is concrete.

Primer 100 is particularly associated with polyurethane sealants while Primer 150 is suited to compatible silicone, hybrid & SMX polymer systems.

For related exterior sealing applications, browse Weatherproofing Supplies.

Trafficable Floor Joints

Warehouse floors, commercial areas & other trafficable joints can experience movement alongside repeated foot, trolley or equipment traffic.

Surface preparation is therefore part of the joint system rather than a cosmetic extra.

On suitable porous joint faces, the appropriate primer can prepare the substrate before compatible Soudal sealants are installed. The joint still needs correct dimensions, backing arrangement & sealant selection—the primer supports the bond rather than replacing proper joint construction.

Bathrooms, Showers & Wet Areas

Wet-area priming has a different purpose from priming the sides of a sealant joint.

Soudaprim DP is designed for porous or absorbent mineral surfaces before compatible liquid waterproofing membranes. Suitable substrates can include concrete, cementitious surfaces, anhydrite & gypsum board where specified.

Its low-viscosity formulation penetrates the surface, binds residual dust, reduces absorption & helps consolidate suitable substrates before the membrane stage.

The important distinction is that Soudaprim DP belongs to the substrate-preparation stage of the waterproofing system. It isn't a replacement for the membrane itself.

Powder-Coated Aluminium

Window frames, façade components & other powder-coated aluminium surfaces present a dense finish rather than an absorbent mineral substrate.

Surface Activator can clean, degrease & promote adhesion on suitable powder-coated aluminium profiles.

Activator Spray 601 provides another fast-drying preparation option developed particularly for regular & textured powder coatings before compatible hybrid, SMX & silicone-based products.

For associated installation components, explore Mounting Hardware.

Plastics & Difficult Non-Porous Surfaces

Some plastics can be challenging bonding surfaces because of their surface characteristics or residues left from manufacturing.

Soudal Surface Activator is intended for selected non-porous substrates including compatible plastics. Activator Spray 601 can also improve adhesion on specified difficult non-porous materials.

Don't assume every plastic behaves the same way. Identify the material where possible & confirm compatibility with both the preparation product & the sealant or adhesive that follows.

Porous & Powdery Mineral Surfaces

A dusty-looking substrate deserves investigation before anything is bonded or waterproofed over it.

Soudaprim DP can be used as preliminary treatment on suitable sandy or powdery mineral substrates. Its penetrating formulation can help bind residual dust, consolidate the surface & reduce absorption.

That doesn't mean primer can rescue unsound construction.

Loose, delaminating, contaminated or badly deteriorated material still requires appropriate remediation. Bonding successfully to the top layer achieves little if that layer can separate from the substrate underneath.

Window & Door Installation

Window & door assemblies can bring aluminium, masonry, plastics, sealants & different surface finishes together within a surprisingly small area.

Treat each bond line separately.

A porous masonry reveal may require a different preparation approach from a powder-coated aluminium frame or plastic component. Correct preparation follows the transition between materials rather than applying one product around the entire opening.

Product Selection Guide

Start With the Substrate, Then Check What Goes Over It

Is the Surface Porous?

This should be one of the first checks.

Porous surfaces absorb liquids into their structure. Concrete, cementitious materials, masonry & gypsum-based substrates are common examples, although actual absorbency varies considerably.

Non-porous surfaces behave differently. Glass, coated metals & many plastics require preparation that works primarily at the bonding interface rather than soaking into the material.

Don't classify a substrate by appearance alone.

A coating can completely change its surface behaviour.

What Goes Over the Primer?

Primer selection doesn't finish when you've identified the substrate.

Ask what will be applied next:

► Polyurethane sealant
► Silicone sealant
► Hybrid or SMX polymer
► Adhesive
► Waterproofing membrane

The preparation product & following material need to form a compatible system.

Is the Surface Actually Sound?

Primer isn't a substitute for repair.

Before application, check for:

► Loose material
► Dust
► Oil or grease
► Existing coatings
► Excess moisture
► Crumbling edges
► Surface contamination
► Release agents on plastics
► Corrosion on metals

If the material you're priming isn't securely attached to the structure, improving adhesion to its upper surface doesn't solve the underlying weakness.

Porous Primer or Surface Activator?

Allow the Preparation Product to Do Its Job

Don't rush the next application simply because the surface looks dry.

Primer or activator needs to be used according to its specified application method, drying conditions & overcoating requirements.

Temperature, ventilation, substrate condition & the individual product can all influence preparation.

Follow the current product instructions rather than applying one universal waiting time across every primer & activator.

Expert Tips

Identify the coating as well as the substrate. “Aluminium” doesn't tell you whether you're dealing with bare, anodised or powder-coated material.

Work backwards from the final product. Before opening the primer, confirm whether the next layer is polyurethane, silicone, hybrid polymer, adhesive or waterproofing membrane.

Don't confuse cleaning with priming. A surface can look clean while still requiring the specified adhesion-promoting treatment.

Remove loose material before trying to consolidate the surface. Primer can support suitable substrate preparation but shouldn't be expected to rebuild failed concrete, plaster or masonry.

Keep prepared surfaces clean. Once a substrate has been cleaned or activated, unnecessary handling can put oils & contamination straight back onto the bond area.

Treat plastics cautiously. Protective films, mould-release residues & the plastic formulation itself can affect adhesion.

Use primer where the system requires it—not everywhere by habit. Unnecessary or incompatible preparation can be just as problematic as skipping a required step.

Prime the actual bond area. Coating surrounding surfaces unnecessarily wastes product & can complicate finishing.

Check environmental conditions. Temperature, moisture & weather exposure can affect preparation & the sealant, adhesive or membrane being installed afterwards.

Test unfamiliar combinations. When the coating, substrate or application is uncertain, a preliminary adhesion or compatibility test is better than discovering a problem after installation.

For crews handling primers, activators, sealants & other construction chemicals, read How to Read a Safety Data Sheet - A Quick Guide for Workshop Operators.

For practical contamination-control & equipment-care advice, see How To Clean Your Gear Without Ruining It.

For a broader perspective on selecting trade products for the job rather than price alone, read The Hidden Cost of 'I Can Get It Cheaper Online.