rotolining

Rotolining is a thermal process that applies a continuous polymer layer to the interior surfaces of hollow metal components by heating and rotating them simultaneously. The object, typically a tank, cylinder, or complex casting, is placed inside a rotating mold or holder and heated while turning at controlled speed. Powdered or liquid polymer material adheres to the inner walls through centrifugal force and thermal fusion, creating a uniform, adherent lining without seams or weak points.

The process works because rotational speed and heat work together: centrifugal acceleration presses the polymer against the interior surface while elevated temperature (typically 150 to 250 degrees Celsius depending on the polymer type) softens the material enough for molecular bonding to the metal substrate. The rotation rate, duration, and temperature must be precisely matched to the polymer's flow characteristics and the vessel's geometry. Common polymers for rotolining include polyethylene, polypropylene, epoxy, and polyester, each chosen for chemical resistance, thermal tolerance, or adhesion requirements.

Industrial applications and advantages

Rotolining is standard for chemical storage tanks, acid digesters, and industrial vessels where internal corrosion or chemical attack would damage bare metal. It also lines cooling system components, bearing housings, and brake drums where wear resistance or thermal isolation matters. The process eliminates joints and overlaps that plague traditional spray coating or manual lining; a single rotolined surface is inherently stronger than a seamed or patched interior. This makes it especially valuable for pressure vessels and containers that cycle thermally or experience vibration.

Common failure modes include poor adhesion (from inadequate surface preparation or temperature mismatch), uneven thickness from unbalanced rotation, and delamination when the lining cools faster than the substrate. The polymer layer typically ranges from 1 to 5 millimeters thick; thicker applications require longer dwell times and higher temperatures, which risk substrate distortion or polymer degradation. Inspection usually involves visual examination and sometimes ultrasonic thickness measurement.

The term reflects the process literally: rotation plus lining. Rotolining sits between spray-on coatings and hand-applied liners in the industrial hierarchy: faster than manual application, more uniform than spraying, but slower and more equipment-intensive than batch dip coating. It is common in chemical manufacturing, water treatment, and heavy equipment building where interior corrosion protection must be reliable and maintenance-free for years.