What "in-place coating" actually means
In-place coating means preparing and coating equipment where it is installed, without removing it from its service environment. The term covers two very different situations: the equipment is shut down but stays on its supports, or it is partly kept running during the work. The first is common; the second is the exception, decided case by case.
The need almost always comes from an access constraint. A tank installed before the building was closed no longer fits through the door. A buried pipe would require excavation. A heat exchanger flanged into a network cannot be removed without stopping the whole line. In those cases the question is not "should we coat in place?" but "under what conditions will the result match shop work?".
What the shop does better — and what the field has to compensate
In a shop, temperature, humidity, dust and part orientation are under control. On site, none of those is given. In-place coating succeeds when shop conditions are rebuilt artificially around the area being treated.
| Variable | In the shop | In place — what has to be put in place |
|---|---|---|
| Surface preparation | Blast booth | Contained blasting with extraction, or spark-free mechanical preparation in classified areas |
| Dew point | Controlled | Continuous measurement; heating or dehumidification of the enclosure |
| Substrate temperature | Stable | Contact probes; local preheating in cold season |
| Contamination | Low | Soluble salt testing before application; protection from process fallout |
| Access to surfaces | Full | Partial: hidden areas are treated with different methods or excluded from scope |
The last row is the one that gets underestimated. A tank floor reachable only through a manway, the underside of a pipe a few centimetres from the ground: those areas can be treated, but with different methods and tolerances. They must appear explicitly in the job definition.
Systems that tolerate field conditions
Not every coating tolerates site conditions. What matters: the application temperature window, tolerance to residual humidity, recoat interval, and time to return to service.
- Surface-tolerant epoxies — formulated to bond on mechanical preparation (SSPC-SP 11 or SP 3) rather than a near-white blast; the most frequent compromise when blasting is impossible.
- Ceramic-filled epoxies — to rebuild thickness lost to erosion and restore a smooth surface in flow paths.
- Polyurethanes and polyureas — fast return to service, attractive when the shutdown window is the dominant constraint; more sensitive to humidity during application.
- Composite wraps — for a pipe or vessel whose remaining wall thickness is in question, under ASME PCC-2 or ISO 24817; they restore mechanical capacity, not only a barrier.
What no system will do, whatever its price: compensate for inadequate surface preparation. Near-white metal blast remains the reference; where it is impossible, the system must be chosen for the preparation actually achievable, not the other way round.
When the equipment stays in service
Treating equipment that keeps running is possible in a limited set of cases: an external repair on a live low-temperature line, a composite reinforcement on an isolated section, an external recoat on a full storage tank. Three conditions must hold at once: the treated surface stays inside the product's temperature window despite the circulating fluid, the fluid does not reach the treated surface, and the preparation method introduces no ignition or contamination risk. If one is missing, the work waits for the shutdown.
Classified areas add their own rules: spark-free preparation, solvent-free or high-flash-point products, a specific work permit. That case is covered in our article on ATEX zone repair without hot work.
Inspecting what cannot be seen
Acceptance of an in-place coating relies on the same measurements as shop work — dry film thickness, holiday detection, pull-off adhesion on a witness area — with one difference: the hard-to-reach areas are precisely the ones inspected least. The acceptance file must therefore state clearly which surfaces were measured and which were not. A report showing an average thickness with no map of measurement points is worth little for buried or confined equipment.
Where in-place coating stops
Three situations where it is better to stop, or change approach:
- The wall loss is structural. A coating protects a surface; it does not restore mechanical strength. If the strength calculation is in question, the answer is a qualified composite reinforcement or replacement, not another layer.
- Contamination cannot be removed. Soluble salts above threshold, oil soaked into concrete, a surface that recontaminates between preparation and application: the coating will disbond, whatever the product.
- The climate window does not exist. Outdoors in cold season, without heated containment, application moves to spring. Forcing the season is the first cause of rework the following year.
Frequently asked questions
Does an in-place coating last as long as shop-applied? It can, if shop conditions were rebuilt — containment, dew point control, verified preparation. Without that, no, and the difference shows from the second year.
Can a tank interior be coated without emptying it completely? Not for an internal lining: the surface must be dry, clean and accessible. An external treatment on a full tank is possible if the wall temperature stays within the product's range.
How long before return to service? It depends on the system: hours for some polyurethanes, several days for a thick epoxy curing fully at low temperature. The interval is fixed when the product is chosen, not at the end of the job.
Is a hot-work permit required for in-place blasting? Abrasive blasting is not hot work in the strict sense, but it generates impact sparks; in classified areas it is replaced by spark-free preparation. The site rules according to its classification.
How do I know whether the equipment is a good candidate? A prior inspection — remaining thickness, surface condition, real access, expected ambient conditions — answers that before any commitment. It is the first step, not an option.
In practice
In-place coating is a real lever when removal is impossible or disproportionate, provided one accepts that it demands more rigour than shop work, not less. Induscoat treats equipment in place across Quebec and Ontario — containment, area-appropriate preparation, documented inspection — as part of its protective coatings service and industrial corrosion protection. For a specific case, the prior inspection is scheduled through the quote request. Technical data sheets for the Induscoat range are published on the brand site, induscoat.com.
Hicham M, P Eng, PMP
Engineer and project manager (PMP) at Induscoat. Over 16 years of experience in industrial coatings, composite repairs and wear protection on mining, energy and petrochemical sites in Canada and internationally.