Corrosion and Thickness Testing: Preparing Crane Components for Assessment

A coating defect is not itself a measured loss of structural thickness. Equally, apparently small surface damage can conceal local pitting or internal corrosion. The assessment should identify the component's function, the likely damage mechanism and the areas where moisture or contaminants collect.

Boom sections, box members, connection plates and drainage details present different inspection problems. A survey planned for a broad, accessible plate may not adequately characterise a narrow crevice or an enclosed member.

The corrosion inspection and thickness testing service can help define the survey before access, cleaning and measurement locations are arranged.

Measured thickness needs a reference. Original drawings, nominal dimensions, material specifications and earlier readings can help establish what has changed. If those records are missing, say so; an assumed original thickness should not quietly become an established fact.

For example, a reading from an accessible outer face may not describe corrosion on a concealed inner face near a drain. An engineer may need additional investigation to assess the relevant load path. A single favourable reading should not be treated as approval of the whole member.

Thickness testing often relies on suitable contact conditions and a technique matched to the material and surface. Heavy scale, loose coatings, roughness or geometry can affect readings. Discuss the cleaning method with the inspector before altering the surface, especially where evidence of cracking or past repair may matter.

Owners should arrange isolation, stable access and access to both drawings and equipment. Entry into enclosed spaces, work at height and removal of covers require their own controls. Do not open structural members or remove metal simply to obtain a reading.

• Mark the asset and affected zones consistently on photographs and drawings.
• Provide previous thickness maps, repair details and environmental exposure history.
• Identify inaccessible surfaces, sealed cavities and areas recently repainted.
• Confirm who supplies access equipment, permits, isolation and agreed cleaning.
• Allow time for follow-up measurements if initial readings are inconclusive.

A useful survey records where measurements were taken, not just a list of numbers. A location grid or annotated drawing allows the same points to be revisited. Local minima, pitting observations and coverage limitations may be more important than an average thickness.

Comparisons require consistent methods and location references. If one survey samples different points from another, an apparent improvement or deterioration may reflect coverage rather than a real change. Keep raw readings and the interpretation together.

There is no universal remaining-thickness percentage that makes every crane component acceptable. Loads, local geometry, fatigue demands, material and manufacturer criteria affect the decision. The competent assessor should explain whether the evidence supports continued use, restrictions, repair, monitoring or replacement.

A thickness report does not by itself assess every possible failure mode. Cracking, distortion and connection condition may need separate attention. Ask the report author which uncertainties remain and how they affect the next inspection or engineering review.