Dr. Fixit Primer AC
The primer coat that gets Dr. Fixit’s roof topcoats to actually stick — to galvanized sheets, old tiles, marble and granite that paint normally slides right off.
What is it?
A single-pack, water-based acrylic-copolymer primer built to do two jobs at once — fight corrosion on galvanized and aluminium roof sheeting, and give slick non-porous surfaces like ceramic tile, marble and granite enough grip for a topcoat to bond to.
Where is it used?
Ageing GI/AC corrugated roof sheets on factory sheds and godowns, tiled or stone-clad terraces and chajjas being recoated rather than re-laid, and metal roof accessories — ridges, gutters, flashings — going under a Dr. Fixit roof topcoat system.
Why use it?
Most roof topcoat failures on galvanized sheets or polished stone trace back to one thing: the surface was never primed, so the coating never really bonded and lifted within a season or two. Primer AC exists to close that gap, backed by actual cross-hatch adhesion (ASTM D3359) and 100-hour salt-spray (ASTM B117) data rather than a marketing claim.
How is it applied?
Dilute with 10% clean water, stir thoroughly, and roll or brush on at 7-8 sq.m per litre per coat. It dries touch-free in 4-6 hours, with a minimum 2-hour overcoat window before the topcoat goes on — best worked between 10°C and 35°C.
About Dr. Fixit Primer AC
If you’ve ever watched a fresh coat of roof paint bubble and peel off an old GI sheet roof within one monsoon, you’ve seen exactly the problem Dr. Fixit Primer AC was built to fix. Galvanized steel, aluminium sheeting, and polished stone or ceramic tile are some of the least forgiving substrates a waterproofing contractor deals with — smooth, often oily or oxidised, and actively resistant to anything applied on top. Primer AC is Pidilite’s answer: a single-component, water-based primer using an acrylic-copolymer binder engineered specifically to key into these surfaces, so that whichever Dr. Fixit roof topcoat goes on next actually has something to hold onto.
In practice this makes it as much a retrofit product as a new-construction one. A large share of the roofing and terrace stock across Delhi NCR is exactly the kind of substrate Primer AC targets — decades-old corrugated sheet roofs on industrial sheds, or terraces finished in ceramic, vitrified tile, marble or granite that owners have no interest in stripping out just to waterproof. Primer AC lets a contractor prime over what already exists, removing a demolition step that would otherwise add cost and downtime to the job. It’s also formulated lead- and chromate-free, making it a genuinely lower-odour, lower-toxicity option for priming work on occupied buildings — schools, hospitals, residential blocks — where a strong solvent-based primer would be a harder sell.
The technical insight
The two numbers worth paying attention to on the datasheet are the 100-hour continuous salt-spray result (ASTM B117) and the ASTM D3359 cross-hatch adhesion rating — both come back “excellent” on mild steel, galvanized steel and aluminium, which is the real evidence behind the anti-corrosive claim, not just a label. Viscosity is quoted at 70-85 KU (ASTM D2042), which is why the sheet calls for a 10% water dilution before rolling: thinner than that and film build suffers, thicker and the 7-8 sq.m/litre coverage rate falls apart. At 50-55 microns dry film thickness it’s a genuinely thin coat, which is also why surface prep matters so much — a primer this thin has no ability to bridge over loose rust, mill scale or old flaking paint, so all of that has to come off mechanically before the primer goes on.
Where it is used
- Priming galvanized and aluminium corrugated roof sheets ahead of a Dr. Fixit roof topcoat
- Recoating old ceramic or vitrified tiled terraces and chajjas without lifting the tiles
- Prepping marble and granite roof or terrace cladding before a protective waterproof topcoat
- Priming cement mosaic tile roofing on older residential buildings
- Recoating GI/AC sheet roofs on factory sheds, warehouses and godowns
- Priming ridge caps, gutters, flashings and other galvanized roof accessories
- Retrofit waterproofing where tile or stone replacement isn’t in the budget
- Prepping podium and terrace decks finished in non-porous stone before elastomeric coating
Key advantages
- Purpose-built adhesion to the substrates paint usually fails on — galvanized steel, marble, granite — backed by ASTM D3359 test data
- Water-based, lead- and chromate-free formulation, so lower odour and safer for work on occupied buildings
- Fast cycle time — touch dry in 4-6 hours, topcoat-ready from as little as 2 hours
- Corrosion resistance is salt-spray tested (100 hrs, ASTM B117), not just claimed
- Single-pack — no catalyst or mixing ratio to get wrong on site
- Wide, forgiving coverage band (7-8 sq.m/litre) that suits crews working across large roof areas
- Engineered specifically to hand off to Dr. Fixit’s own roof topcoats, so the primer-to-topcoat bond isn’t a guess
- 24-month shelf life gives contractors room to stock ahead of phased jobs
Limitations & considerations
- It’s a bonding and anti-corrosion prep coat only — it carries no waterproofing membrane thickness or crack-bridging of its own
- Sold only in 20-litre pails — there’s no small pack for a single patch or touch-up job
- Needs a genuinely degreased, de-rusted, dust-free substrate; any shortcut on surface prep undoes the adhesion benefit
- Application is temperature-bound (10°C-35°C) — not something you can force through in peak summer midday heat or a cold early morning
- Formulated for galvanized/aluminium metal and non-porous stone/tile specifically — not a general masonry, wood or plastic primer
- Published performance data is for use under Dr. Fixit’s own roof topcoat range; pairing it with a third-party topcoat isn’t something the datasheet vouches for
Selection & best practice
Surface prep decides whether this primer works or not. On galvanized sheets, wire-brush off rust, moss and old paint back to sound metal, tighten or replace any stripped fasteners, and seal panel seams with a proper joint sealant, giving it a full 72 hours to cure before priming over it. On tiled or stone terraces, pressure-wash off grime and mildew, re-fix any loose or debonded tiles, and grout open joints — an epoxy grout works well here — before priming. Once the substrate is ready, dilute Primer AC with 10% clean water and stir it well; don’t eyeball the dilution, since going thicker than spec chokes the 7-8 sq.m/litre coverage and going thinner starves the film build. Roll or brush it on evenly, respect the minimum 2-hour overcoat gap (4-6 hours is safer in humid weather), and try to keep the whole sequence — prime to topcoat — within a single dry-weather window so an unexpected shower doesn’t wash out an undercured film.
Specifications
| Chemistry / System | Single-component, waterborne acrylic-copolymer anti-corrosive primer (lead & chromate-free) |
| Colour | Grey |
| Solid Content | Min. 52% |
| Specific Gravity | 1.22 – 1.28 |
| Viscosity (@25°C) | 70 – 85 KU (ASTM D 2042) |
| Dry Film Thickness | 50 – 55 microns per coat |
| Coverage | 7 – 8 sq.m per litre per coat |
| Adhesion & Corrosion Resistance | Excellent per ASTM D 3359 (MS, GI, Aluminium); passes 100-hr salt spray per ASTM B 117 |
| Pack Size / Shelf Life | 20 litres; 24 months from date of manufacture, unopened |
Industry use cases
Residential terrace retrofit
An old ceramic-tiled terrace with failed grout and seepage gets Primer AC over the existing tile instead of a full tear-off, so a Dr. Fixit topcoat can go straight on and the leak gets fixed in days, not weeks.
Industrial & warehouse roofing
Ageing GI corrugated sheet roofs on factory sheds get de-rusted, seam-sealed and primed with Primer AC before recoating — extending roof life without the cost of re-sheeting the whole structure.
Institutional buildings
Marble- or granite-clad terraces on schools and hospitals get primed with a low-odour, water-based coat that’s compatible with work happening around an occupied building.
Residential bungalows with mosaic tile roofs
Older Delhi NCR bungalows finished in cement mosaic roof tiles get a fresh, waterproofed finish without disturbing the original tile.
Commercial podium decks
Stone-finished podium and terrace decks on commercial complexes are primed ahead of an elastomeric waterproof topcoat as part of a full building-envelope upgrade.
Frequently asked questions
Will Primer AC waterproof my roof on its own?
Can I prime straight over rusted GI sheets without cleaning them?
How long before I can apply the topcoat after priming?
Does it work over old ceramic or vitrified tiles without removing them?
What pack sizes does it come in?
Is it safe to use while the building is occupied?
How we position Dr. Fixit Primer AC
Primer AC’s job inside the Dr. Fixit range is narrow and specific: it’s the substrate-prep step that sits between an existing galvanized or non-porous surface and Dr. Fixit’s own roof topcoat system, which is what it’s engineered to hand off to. For different substrates, Dr. Fixit itself offers other primers — Torchshield Primer is the equivalent prep coat for torch-applied bituminous membranes, and Pidiprime A serves the tile-fixing and sealant side of the range — so the right primer choice really depends on what’s underneath, not just the brand. Fosroc doesn’t carry a direct like-for-like SKU for this specific galvanized-metal-plus-non-porous-tile niche; a specifier working purely on structural steel ahead of a protective coating might look at Fosroc’s Nitoprime range of primers instead, but for roof recoating over old tile, stone or GI sheet, Primer AC remains the more purpose-built option. As an authorised Dr. Fixit distributor and applicator, Space Arc supplies Primer AC as part of a full, warranty-backed prime-to-topcoat roofing system rather than as a standalone tin, which is the detail that actually matters on a roof recoat job.
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