Every drill hole you make damages the corrosion protection system. That's not negotiable. The Grenadier ships with a comprehensive corrosion protection process applied by INEOS. When you modify it — drilling, welding, cutting, removing panels — you're creating new rust vectors. You must restore protection to factory standard.
The Restoration Process
Restoring corrosion protection after drilling follows a fixed sequence:
| Step | Action | Purpose | Product Type |
|---|---|---|---|
| 1 | Deburr | Remove sharp edges and debris | Deburring tool or fine file — ensure no metal shavings remain in cavity |
| 2 | Degrease | Clean area of oils and residue | Wax and grease remover (solvent-based). Isopropyl alcohol for light cleaning. Surface must be completely dry before next step. |
| 3 | Phosphate prime | Chemical bond to bare steel for base corrosion resistance | Zinc phosphate primer or etch primer. Self-etching primers (acid-based) are preferred for field application — they chemically bond to bare steel without sandblasting. Apply within hours of degreasing to prevent flash rust. |
| 4 | Paint | Location-appropriate coating | Underbody/chassis: Rubberised underbody coating or chassis-specific paint (black, satin). Body panels: Match factory colour. INEOS paint codes available through dealers — request the exact code for your colour/year. Interior/hidden: Any zinc-rich primer topcoat is acceptable. |
| 5 | Seal | Cavity sealant to prevent moisture entrapment | Cavity wax (waxy injection-type sealant) for hollow sections. Seam sealer for panel joints and visible edges. Must be non-hygroscopic and water-repellent. |
This isn't a shortcut process. Every drilled hole, every welded joint, every cut panel edge requires this sequence or it will rust.
Dissimilar Metals and Galvanic Corrosion
If you're attaching fasteners made of different metals — steel bolts on aluminium brackets, for example — install insulating washers, bushings, or sleeves at the contact point. Dissimilar metals create galvanic corrosion when moisture is present. The fastener and substrate effectively form a battery.
The Grenadier uses a combination of steel frame, aluminium body panels, and various alloy brackets. This makes galvanic corrosion a constant concern for any modification that joins components.
Galvanic Corrosion Risk Table
The further apart two metals are on the galvanic series, the faster corrosion occurs at their junction. Here are the most common pairings encountered when modifying a Grenadier:
| Metal Pairing | Risk Level | Where You'll Encounter It | Prevention |
|---|---|---|---|
| Steel bolt → Aluminium panel | High | Mounting accessories to body panels, attaching brackets to aluminium skin | Insulating washer + nylon bush around bolt shank. Tef-Gel or anti-seize compound on threads. |
| Stainless steel bolt → Steel frame | Moderate | Aftermarket brackets bolted to chassis, skid plate mounting | Anti-seize compound on threads. Stainless is cathodic to mild steel — the frame corrodes preferentially at the contact point. |
| Aluminium bracket → Steel frame | High | Aftermarket light brackets, antenna mounts, accessory rails on the frame | Full isolation: insulating washers top and bottom, nylon sleeve around fastener, no metal-to-metal contact. |
| Zinc-plated bolt → Aluminium | Low–Moderate | Factory-style fasteners on aluminium components | Zinc is closer to aluminium on the galvanic series. Lower risk, but still apply anti-seize in wet environments. |
| Copper wiring/terminals → Aluminium | High | Electrical connections on aluminium body panels, ground straps | Use tinned copper terminals. Apply dielectric grease. Never leave bare copper on bare aluminium. |
| Carbon fibre → Any metal | Very High | Aftermarket carbon fibre panels or accessories mounted to any metal surface | Carbon fibre is extremely cathodic. Full insulation mandatory — fibreglass isolation layer between carbon and metal. |
Galvanic Isolation
When joining dissimilar metals (e.g., steel to aluminium), insulating components are mandatory:
- Insulating washers between bolt head and surface
- Insulating bushings/sleeves around bolt shank
- No direct metal-to-metal contact between dissimilar materials
- Anti-seize compound (Tef-Gel or similar) on all threads — prevents galling and provides an additional moisture barrier
- Failure to isolate will cause accelerated corrosion at the joint
Coastal and Desert Environments
Where you drive determines how aggressively corrosion attacks your modifications. Standard protection may be adequate in temperate climates but insufficient in extreme environments:
Coastal / Salt-Exposed Vehicles
- Salt water accelerates galvanic corrosion by 5–10x compared to fresh water
- Every modification point must be treated as high-risk regardless of metal pairing
- Apply cavity wax to all hollow sections — including inside frame rails where you've drilled
- Wash the underbody with fresh water after every salt water or beach sand exposure
- Inspect all modification points every 3–6 months for early signs of corrosion (white powder on aluminium, orange rust on steel)
- Consider a full underbody oil-based rust treatment annually — it penetrates seams and crevices that paint cannot reach
- Electrical connections are especially vulnerable: use marine-grade heat-shrink and dielectric grease on every terminal
Desert / Arid Environments
- Low humidity reduces galvanic corrosion risk — but doesn't eliminate it. Morning dew and occasional rain concentrate salt from dust and soil
- The primary enemy is abrasion: sand and grit strip protective coatings from exposed surfaces
- Rubberised underbody coating takes the worst of it — inspect for chips and reapply where abraded
- Stone guard film or additional rubberised coating on any bracket or mount in the wheel spray zone
- UV degrades rubber seals and flexible sealants faster — inspect and replace weather seals around modification points annually
- Thermal cycling (extreme heat by day, cold at night) stresses sealant joints. Use flexible, temperature-rated sealants that won't crack
Whether you're running coastal trails or desert tracks, the modifications you make with DVA Mechanics accessories — crossbars, utility belts, rear carriers — are designed with proper corrosion isolation in mind. But the mounting points you create in the vehicle still need your attention.
Cavity Sealant and Drain Openings
All drilled holes must be sealed from inside the frame with cavity sealant. Standard drain openings must be retained — don't seal them. They exist so water doesn't trap inside the structure.
Non-hygroscopic, non-water-retentive, water-repellent insulation materials are required everywhere.
Chromium 6 Prohibition
Surface protection cannot contain hexavalent chromium (Cr6), banned since July 2007 under EU Directive 2000/53/EC.
Bolt Connections
Corrosion protection at bolt connections requires using fasteners with a tested friction coefficient (µ value). Micro-encapsulated adhesive is recommended — it fills microscopic gaps and prevents moisture ingress while allowing future disassembly.
Post-Welding
After all welding, apply corrosion protection immediately. Phosphating is recommended as base coating. Don't let the weld sit overnight unprotected.
The Grenadier arrives from INEOS with a standardised preservation process. Your job as body builder is to maintain equivalent protection. If you don't know what INEOS used, ask them.
Product Recommendations by Protection Step
Matching the factory's three-layer corrosion protection (E-coat, powder coating, hot wax) after modifications requires specific products at each stage. Here's what experienced Grenadier builders are using:
Step-by-Step Product Guide
| Protection Stage | Product Type | Application |
|---|---|---|
| Bare metal prep (after drilling/cutting) | Zinc-rich cold galvanising spray (e.g., zinc phosphate primer) | Apply within 30 minutes of exposing bare metal |
| Primer coat | Epoxy primer or etch primer | 2 coats minimum, full cure before topcoat |
| Topcoat | 2K polyurethane or powder coat (if possible) | Colour-match or use satin black for underbody |
| Cavity protection | Wax-based cavity sealant (spray-in) | Flood all enclosed box sections after modification |
| Fastener protection | PTFE-based anti-seize (e.g., Tef-Gel) | Apply to all bolt threads and contact surfaces |
| Underbody touch-up | Rubberised underbody coating | Over-spray modified areas after primer cures |
Galvanic Corrosion: The Dissimilar Metals Problem
The Grenadier uses a galvanised steel body on a steel ladder frame with aluminium closures (doors, bonnet, tailgate). This mix of metals creates galvanic corrosion risk at every junction — and aftermarket accessories introduce additional metals into the equation.
| Metal Combination | Galvanic Risk | Mitigation |
|---|---|---|
| Steel bolt into aluminium panel | High | Isolating washer + PTFE gel on threads |
| Stainless steel bracket on galvanised steel | Medium | Nylon isolation pad between surfaces |
| Aluminium bracket on aluminium door | Low | Same-metal pairing — minimal risk |
| Bare steel bracket on aluminium | High | Powder coat bracket + isolating washer + sealant |
| Copper wiring against aluminium | High | Rubber grommets, no direct metal contact |
What Owners Are Discovering
"Spotted corrosion under the paint coat on the left-hand rear door. Looks like another thing to get sorted."
— Grenadier owner reporting paint bubbling, The INEOS Forum, January 2026
"Looks galvanic. The hinge is steel as well as the fixing, but the door is aluminium."
— Forum member diagnosing the corrosion mechanism, The INEOS Forum
"Get some Ultra Tef-Gel. It's basically a PTFE Teflon thick gel that you apply as both a lubricant and to prevent galvanic corrosion. Since the Grenadier is a combination of both aluminium and steel, bolt-on mods may be made of dissimilar metals."
— Experienced owner recommending fastener protection, The INEOS Forum, May 2024
"Echoes of pre-2015 Defenders… Those of us in New England who bought NAS Defenders from new may recall that the doors were routinely replaced under warranty in the first three years."
— Long-time off-road vehicle owner drawing parallels, The INEOS Forum
Coastal and Desert-Specific Advice
- Coastal environments (salt spray): Rinse the underbody after every beach trip. Apply additional wax-based underbody protection every 6 months. Inspect all fasteners for white aluminium oxide powder — the early sign of galvanic attack.
- Desert environments (sand abrasion): Sand strips protective coatings mechanically. After extended desert use, inspect all underbody coatings and touch up any chips or wear-through. Pay special attention to the area around the exhaust heat shields where sand collects.
- Salt road regions (winter): Annual underbody cavity wax treatment is essential. Factory hot wax degrades over time, especially in areas disturbed by modifications. Treat modified areas more frequently than factory-original sections.
DVA Mechanics designs all bolt-on accessories with corrosion isolation built in — stainless steel fasteners with nylon isolation washers and pre-applied thread sealant. This isn't a detail — it's a design principle that prevents the galvanic problems owners are already encountering on modified Grenadiers.
