6. Corrosion Assessment Tool

9. Thin Gauge steel pressings

12. Method of repair

The corrosion assessment tool must be used carefully to avoid unnecessary damage. The tool comprises

- A durable engineering plastic head for light tapping, and

- An aluminium alloy shaft with a curved 'spade end' for light scrapping. The alloy shaft can also be used as a small lever

WARNING

The curved spade end must only be used for light scrapping and not to prod and poke the vehicle structure.

In some vehicles, comparatively thin gauge steel pressings are used for certain steering and suspension components, mountings, sub-frames and crossmembers.

Many of these parts have hollow sections or upfacing areas in which road dirt impregnated with salt or other chemicals collects causing serious but often very localised corrosion.

In some cases where large amounts of salt are used on roads, corrosion has caused the failure of steering and suspension components within three years. Some components have been known to fail completely at one end and still be undamaged at the other.

It is essential that repairs to corroded areas are properly carried out. Only welding is acceptable for repairs to 'prescribed areas'.

Suitable materials of appropriate gauge and thickness should be used for repairs so that

- Any plating or welding extends to a sound part of a load bearing component, and

- The repair must be virtually as strong as the original structure

So only a continuous seam weld is acceptable for patch repairs, (even if the patch extends beyond the prescribed area) although spot welded joints are acceptable where they originally existed. (provied the original defective panel flange has been removed)

Stitch or plug welding is acceptable as an alternative to spot welding in these cases.

Welded repairs to highly stressed components such as steering/suspension arms, rods, levers etc are not normally acceptable.

7. Safety precautions

10. Platform or underframe

Eye protection is recommended when assessing corrosion in vehicle structures and components. Any sharp edges on the corrosion assessment tool should be removed.

Some vehicle types (such as VW 2Beetle" etc) have bodies and various mechanical parts attached to a platform or underframe which is the main load bearing structure. Defective body panels considered to be part of a load bearing structure should only be rejected if they

a. play an active part in directly supporting the steering, suspension, braking components or seat belt anchorages, or

b. Are likely to adversely affect the correct functioning of the braking system or steering gear (eg by fouling a wheel)

8. General Guidance

11. Corrosion around drainage holes

Corrosion which has not reduced the metal thickness sufficiently to weaken it will clearly not warrant rejection. Howeve, the tester should inform the vehicle presenter that corrosion has started.

On the other hand, where there is severe corrosion, it may be necessary to refuse to carry out a brake test if this could cause danger or further damage.

Corrosion can be more prevalent in areas around drainage holes due to the ingress of moist air, dirt, road salt etc. Therefore special attention should be paid to these areas of the important structural and testable components.

Issue Date: 10th January 2005